Novel conjugates of polymers having a therapeutically active agent and an angiogenesis targeting moiety attached thereto and uses thereof in the treatment of angiogenesis related diseases

ABSTRACT

Conjugates of a polymer having attached thereto an angiogenesis targeting moiety and a therapeutically active agent such as an anti-cancer agent or anti-angiogenesis agent, and processes of preparing same are disclosed. 
     Pharmaceutical compositions containing these conjugates and uses thereof in the treatment of angiogenesis-related medical conditions such as cancer and cancer metastases are also disclosed.

FIELD AND BACKGROUND OF THE INVENTION

The present invention, in some embodiments thereof, relates to novelchemical conjugates and to uses thereof in therapy and diagnosis and,more particularly, but not exclusively, to novel conjugates of polymershaving attached thereto an angiogenesis targeting moiety and ananti-angiogenesis agent and to uses thereof in monitoring and treatingmedical conditions associated with angiogenesis.

Angiogenesis is a biological process that involves the sprouting of newblood vessels from pre-existing ones and plays a crucial role in diseasedevelopment and progression. Angiogenesis is a complex process in whichendothelial cells serve as a building block for blood vessel expansion.This process involves an extensive interplay among cells, growthfactors, and extracellular membrane (ECM) components. It is regulatedthrough a fine balance between pro-angiogenic and anti-angiogenicmolecules.

Pathological angiogenesis has been demonstrated in several diseases,including atherosclerosis, cancer, hypertension, rheumatoid arthritis,diabetes and diabetes related complications such as diabeticretinopathy. Tumor growth and metastasis are particularly dependent onthe degree of angiogenesis. Tumor angiogenesis is the proliferation of anetwork of blood vessels that penetrate into cancerous tumors in orderto supply nutrients and oxygen and remove waste products, thus leadingto tumor growth. Tumor angiogenesis involves hormonal stimulation andactivation of oncogenes, expression of angiogenic growth factors,extravasation of plasma protein, deposition of a provisional ECM,degradation of ECM, and migration, proliferation and elongation ofendothelial capillaries.

Inhibition of further vascular expansion has therefore been the focus ofactive research for cancer therapy. Many drugs have been developed,which target different steps in this multi-step tumor angiogenesisprocess. However, most of these drugs were shown to be cytostatic ratherthan cytotoxic and thus do not cause a substantial reduction of tumorvolume during the first stage of treatment.

There are currently eight approved anti-cancer therapies with recognizedantiangiogenic properties. These agents, which interrupt critical cellsignaling pathways involved in tumor angiogenesis and growth, can bedivided into two primary categories: (1) monoclonal antibodies directedagainst specific proangiogenic factors and/or their receptors; (Avastin,Erbitux, Vectibix, Herceptin) and (2) small molecule tyrosine kinaseinhibitors (TKIs) of multiple proangiogenic growth factor receptors(Tarceva, Nexavar, Sutent, Iressa). Inhibitors of mTOR (mammalian targetof rapamycin) represent a third, smaller category of antiangiogenictherapies with one currently approved agent (Torisel). In addition, atleast two other approved angiogenic agents may indirectly inhibitangiogenesis through mechanisms that are not completely understood(Velcade, Thalidomide/Celgene)

The first FDA-approved angiogenesis inhibitor, Bevacizumab (Avastin,Genentech) a monoclonal antibody to vascular endothelial growth factor(VEGF), has recently been approved for metastatic colon cancer treatmentin conjunction with standard conventional chemotherapy.

The largest class of drugs that block angiogenesis are themulti-targeted tyrosine kinase inhibitors (TKIs) that target the VEGFreceptor (VEGFR). These drugs such as sunitinib (Sutent, Pfizer),Sorafenib (Nexavar, Bayer/Onyx Pharmaceuticals) and Erlotinib (Tarceva,Gennentech/OSI/Roche) have the advantages of hitting multiple targets,convenient oral administration, and cost effectiveness. While thesedrugs exhibit promising efficacy, their use is limited by their lack oftarget specificity, which leads to unexpected toxicity [Cabebe et al.Curr Treat Options Oncol 2007; 8:15-27].

Tumor endothelial cells are drug sensitive for long time periods and maybe treated with cytotoxic agents in an “anti-angiogenic dosingschedule”. This dosing schedule involves the administration ofchemotherapy in low doses, well below the maximum tolerated dose (MTD),in close intervals for extended periods of time (“metronomic dosing”).As a result, acute toxicity should be avoided and the drugs may beadministered during longer periods, eventually converting cancer to achronic manageable disease.

The microtubule-interfering agent Paclitaxel (PTX) is a clinicallywell-established and highly-effective anti-neoplastic drug used as amonotherapy and in combination therapy mainly for the treatment ofprostate, breast, ovarian, and non-small cell lung cancers and it is thedrug of choice for the treatment of metastatic breast cancer. It hasalso shown anti-angiogenic and pro-apoptotic properties [Oldham et al.2000 Int. J. Oncol. 16:125-132]. However, due to the hydrophobic natureof the drug, solubilizing agents such as Cremophor EL or ethanol arerequired for its administration. PTX causes severe adverse side effectssuch as neutropenia, neuropathies, and when solubilized in Cremophor ELcauses hypersensitivity reactions. In addition, only a small amount ofthe drug localizes in the tumor and the drug is substrate to effluxpumps in particular p-glycoprotein, resulting in multiple drugresistance.

Water-soluble copolymers such as hydroxypropyl methacrylate (HPMA) andPGA are biocompatible, non-immunogenic and non-toxic carriers thatenable specific delivery into tumor tissue (Satchi-Fainaro et al. NatMed 2004; 10: 255-261). These macromolecules do not diffuse throughnormal blood vessels but rather accumulate selectively in the tumor sitebecause of the enhanced permeability and retention (EPR) effect. Thisphenomenon of passive diffusion through the hyperpermeableneovasculature and localization in the tumor interstitium is observed inmany solid tumors for macromolecular agents and lipids.

Conjugation of anti-cancer drugs to copolymers, such as HPMA or PGA, hasbeen suggested so as to restrict the passage through the blood brainbarrier and to prolong the circulating half-life of the drugs, henceinhibiting the growth of tumor endothelial and epithelial cells byexposing the cells to the conjugated drugs in the circulation for alonger time compared to the free drugs.

U.S. Pat. No. 6,884,817 teaches compositions comprising achemotherapeutic and/or anti-angiogenic drug, conjugated to awater-soluble polyamino acid or soluble metal chelator. The taughtcompositions provide water soluble taxoids which overcome the drawbacksassociated with the insolubility of the drugs themselves, and furtherimprove the delivery of the drugs to tumor tissue and affect acontrolled release of the conjugated drug. According to the teachings ofin U.S. Pat. No. 6,884,817, an exemplary such conjugate of theanti-cancer drug paclitaxel and polyglutamate, exhibited superiorantitumor activity together with a reduced level of toxicity, ascompared with the anti-tumor agent paclitaxel alone.

The conjugate paclitaxel-polyglutamate OPAXIO™ (paclitaxel poliglumex,CT-2103) (Formerly known as XYOTAX™) showed promising results in phaseIII trials and is currently being evaluated for marketing approval.

U.S. patent application Ser. No. 12/117,678 having publication No.2008/0279778 also teaches polyglutamate polymers conjugated to aplurality of drugs for use in drug targeting, stabilizing and imagingapplications. A HPMA copolymer conjugate of paclitaxel has also beendescribed by Meerum Terwogt et al. [Anticancer drugs 2001; 12:315-323].This conjugate was aimed at improving drug solubility and providingcontrolled release of paclitaxel. In this conjugate, the paclitaxel islinked to the HPMA copolymer through an ester bond, and is hencereleased from the polymer by non-tissue specific hydrolytic or enzymatic(esterases) degradation of the ester bond, thereby inducing the commonlyobserved toxicities of paclitaxel.

WO 03/086382 teaches conjugates of water-soluble polymers and theanti-angiogenesis agent TNP-470, and their use as anti-tumor agents, inparticular their use as carriers of TNP-470 into tumor vessels, andtheir effect on the neurotoxicity of TNP-470. According to the teachingsof WO 03/086382, an exemplary such conjugate, HPMA-(TNP-470) conjugate(caplostatin), exhibited superior antitumor activity together with areduced level of toxicity, as compared with TNP-470 alone.

WO 03/086178 teaches a method for decreasing or inhibiting disordersassociated with vascular hyperpermeability by the administration of aneffective amount of an anti-angiogenesis compound or a compound capableof increasing cell-cell contacts by stabilizing tight junction'scomplexes and increasing contact with the basement membrane. Thecompounds taught by WO 03/086178 are endostatin, thrombospondin,angiostatin, tumastatin, arrestin, recombinant EPO, and polymerconjugated TNP-470. According to the teachings of WO 03/086178, anexemplary such conjugate, HPMA-(TNP-470) inhibited vascular endothelialgrowth factor (VEGF)-induced vessel hyperpermeability and inhibitedendothelial cell mediated angiogenesis both in vitro and in vivo.

Integrins are a class of receptors involved in the mechanism of celladhesion. Alterations in the function of these receptors are responsiblefor the occurrence of a number of pathologic manifestations, such as,for example, defective embryogenesis, blood coagulation, osteoporosis,acute renal failure, retinopathy and cancer, particularly metastasis.Since the 1980s it is well recognized that integrins play a key role incell matrix interactions and hence in angiogenesis.

The integrins are heterodimeric transmembrane glycoproteins that composea diverse family of 19α and eight β subunits. An integrin with awell-characterized involvement in angiogenesis and tumor invasiveness isα_(v)β₃. The α_(v)β₃ integrin is a molecular marker that differentiatesnewly formed capillaries from their mature counterparts. This integrinis expressed in various malignant tumors. Inhibition of the α_(v)β₃mediated cell matrix interaction leads to apoptosis of activatedendothelial cells and to disruption of blood vessel formation. Incontrast, α_(v)β₃ is not strongly expressed on quiescent endothelialcells, thus treatment with α_(v)β₃ antagonists does not affectpre-existing blood vessels [Brooks et al. Science 1994; 264:569-571].

α_(v)β₃ integrins therefore play an important role in adhesion,motility, growth and differentiation of endothelial cells. α_(v)β₃integrins are known to bind the RGD sequence (Arg-Gly-Asp; SEQ ID NO:1),which constitutes the recognition domain of different proteins, such aslaminin, fibronectin and vitronectin. The RGD sequence represent theminimal amino acid domain, in several extracellular matrix proteins,which has been demonstrated to be the binding site of the transmembraneintegrins proteins family [Bazzoni et al. 1999, Current Opinion in CellBiology; (11) pp. 573-581]. Indeed it was shown that replacement of evena single amino acid of this short sequence results in loss of bindingactivity to integrins. Integrins mediates the attachment of endothelialcells to submatrix proteins that form the basement membrane of thecapillary. Although all endothelial cells use the integrin to anchor tothe extraluminal submatrix, the α_(v)β₃ integrins are found on theluminal surface of the endothelial cell only during angiogenesis. Thus,agents that target this integrin actually target endothelial cellsinvolved in angiogenesis.

The α_(v)β₃ integrin is overexpressed on proliferating endothelial cellssuch as those present in growing tumors, as well as on some tumor cellsof various origins. Expression of endothelial α_(v)β₃ integrin receptorin aggressive breast carcinomas and glioblastomas is a marker of poorprognosis.

It has been demonstrated that RGD-containing peptides, either isolatedfrom phage peptides library or biochemically synthesized, were able tocompete with extracellular matrix proteins on binding to integrins[Haubner et al. 1997, Angew. Chem. Int. Ed. Engl.; (36) pp. 1374-1389].Tumor-induced angiogenesis can be targeted in vivo by antagonizing theα_(vβ) ₃ integrin with small peptides containing the RGD amino acidsequence.

It has been further found that the substrate specificity ofRGD-containing peptides results from the different conformations of theRGD sequence in different matrix proteins. For example, the bis-cyclicpeptide E-[c(RGDfK)₂] (SEQ ID NO:2) is a ligand-based vascular-targetingagent that binds to integrin α_(v)β₃.

Encoded by a growth factor-inducible immediate-early gene, Cyr61 (alsoknown as CCN1) is a cysteine-rich matricellular protein that supportscell adhesion and induces adhesion signaling. Furthermore, Cyr61stimulates endothelial cell migration and enhances growth factor inducedDNA synthesis in culture and therefore induces angiogenesis in vivo.Mechanistically, Cyr61 acts as a non-RGD-containing ligand of integrinreceptors. Functional blockade of α_(v)β₃, a Cyr61 integrin receptor, isspecifically cytotoxic towards Cyr61-overexpressing breast cancer cellsand a specific α_(v)β₃-RGD peptidomimetic agent prevents α_(v)β₃ frombinding to its ligand, Cyr61.

Cyr61 plays a key role in both the maintenance and the enhancement of amalignant phenotype in breast cancer. Cyr61 is overexpressed in about30% of invasive breast carcinomas, whereas Cyr61 expression levels innormal breast tissues are negligible. It has been recently shown thatCyr61 overexpression can render human breast cancer cells highlyresistant to Paclitaxel. Pharmacological interference with theCyr61/α_(v)β₃ interaction fully restores Paclitaxel efficacy in Cyr61overexpressors, thus implying that a previously unrecognizedCyr61/α_(v)β₃-driven cellular signaling actively modulates breast cancercell growth and chemosensitivity.

Chen et al. reported [J. Med. Chem. 2005; 48:1098-1106] the synthesisand antitumor activity of paclitaxel (PTX) conjugated with a bis-cyclicRGD (E[RGDyK]2) (SEQ ID NO:3) in a metastatic breast cancer cell line.

Mitra et al. report [Journal of Controled Release 2006; 28: 175-183] thebiodistribution and tumor targeting properties ofN-(2-hydroxypropyl)methacrylamide (HPMA) copolymer based conjugates ofmono-(RGDfK) (SEQ ID NO:4) and doubly cyclized (RGD4C; SEQ ID NO:5)α_(v)β₃ binding peptides.

WO 2006/012355 teaches an anti-angiogenic polymer conjugate (APC) fortreatment of solid tumors comprising a chemical moiety targetingcell-surface proteins of endothelial cells at an angiogenic site. Thechemical moiety taught in the application may be a ligand such as RGD4C(SEQ ID NO:5) or RGDfK (SEQ ID NO:4) for a cell-surface receptor, suchas, for example, an integrin. The polymer conjugate taught by WO2006/012355 may further comprise at least one side chain comprising achelator capable of chelating a pharmaceutically acceptable radioactivelabel. The scintigraphic images and biodistribution of an exemplary suchconjugate, HPMA copolymer-RGD4C-^(99m)Tc conjugate (SEQ ID NO: 6),indicated specific in vivo tumor targeting as well as prolongedretention of the conjugate at the tumor site. Treatment of SCID micebearing DU145 human prostate carcinoma xenografts with another exemplaryconjugate, HPMA copolymer-RGD4C comprising the beta particle emitter ⁹⁰Y(SEQ ID NO:7), resulted in significant decrease of tumor volume ascompared to the control (also reported by Mitra et al. in [NuclearMedicine and Biology 2006; 33:43-52])

Wan et al. [2003 Proc. Int'l Symp. Control. Rel. Bioact. Mater. Vol 30:491-492] teach targeting endothelial cells using HPMAcopolymer-doxorubicin-RGD conjugates (SEQ ID NO:8).

SUMMARY OF THE INVENTION

The present inventors have designed and successfully prepared andpracticed conjugates comprised of a polymeric backbone having attachedthereto an angiogenesis targeting moiety and a therapeutically activeagent such as an anti-cancer agent or anti-angiogenesis agent. Theseconjugates were shown to exhibit a potent activity as agents for thetreatment of medical conditions associated with angiogenesis such ascancer and cancer metastases.

According to an aspect of embodiments of the invention there is provideda conjugate comprising a polymeric backbone having attached thereto atherapeutically active agent and an angiogenesis targeting moiety, theangiogenesis targeting moiety comprising a least one Arg-Gly-Asp(RGD)-containing moiety (SEQ ID NO:1), and the therapeutically activeagent being selected from the group consisting of paclitaxel andTNP-470.

According to some embodiments of the invention, the polymeric backboneis derived from a polyglutamic acid (PGA).

According to some embodiments of the invention, the polymeric backboneis derived from a polymer selected from the group consisting of dextran,a water soluble polyamino acid, a polyethylenglycol (PEG), apolyglutamic acid (PGA), a polylactic acid (PLA) apolylactic-co-glycolic acid (PLGA), a poly(D,L-lactide-co-glycolide)(PLA/PLGA), a poly(hydroxyalkylmethacrylamide), a polyglycerol, apolyamidoamine (PAMAM), and a polyethylenimine (PEI).

According to an aspect of embodiments of the invention there is provideda conjugate comprising a polymeric backbone having attached thereto atherapeutically active agent and an angiogenesis targeting moiety, theangiogenesis targeting moiety comprising a least one Arg-Gly-Asp(RGD)-containing moiety (SEQ ID NO:1), and the therapeutically activeagent being selected from the group consisting of an anti-angiogenesisagent and an anti-cancer agent.

According to some embodiments of the invention, the RGD-containingmoiety (SEQ ID NO:1) is an oligopeptide.

According to some embodiments of the invention, the oligopeptide isselected from the group consisting of a cyclic oligopeptide and a linearoligopeptide.

According to some embodiments of the invention, the angiogenesistargeting moiety comprises at least two RGD-containing moieties (SEQ IDNO:1), the moieties being the same or different.

According to some embodiments of the invention, the cyclic oligopeptideis c[Arg-Gly-Asp-Phe-Lys] (SEQ ID NO:9).

According to some embodiments of the invention, the polymeric backboneis derived from a polymer selected from the group consisting of dextran,a water soluble polyamino acid, a polyethylenglycol (PEG), apolyglutamic acid (PGA), a polylactic acid (PLA) apolylactic-co-glycolic acid (PLGA), a poly(D,L-lactide-co-glycolide)(PLA/PLGA), a poly(hydroxyalkylmethacrylamide), a polyglycerol, apolyamidoamine (PAMAM), and a polyethylenimine (PEI).

According to some embodiments of the invention, at least one of thetherapeutically active agent and the targeting moiety is attached to thepolymeric backbone via a linker.

According to some embodiments of the invention, the linker is abiodegradable linker.

According to some embodiments of the invention, the biodegradable linkeris selected from the group consisting of a pH-sensitive linker and anenzymatically-cleavable linker.

According to some embodiments of the invention, the biodegradable linkeris an enzymatically cleavable linker.

According to some embodiments of the invention, the enzymaticallycleavable linker is cleaved by an enzyme which is overexpressed in tumortissues.

According to some embodiments of the invention, the linker comprises a-[Gly-Phe-Leu-Gly]moiety (SEQ ID NO: 10).

According to some embodiments of the invention, the linker comprises-[Gly-Pro-Leu-Gly-Ile-Ala-Gly-Gln]-(SEQ ID NO: 11).

According to some embodiments of the invention, at least one of thetherapeutically active agent and the angiogenesis targeting moiety isattached to the polymeric backbone and/or to the linker via a spacer.

According to some embodiments of the invention, the anti-angiogenesisagent is Paclitaxel and the angiogenesis targeting moiety comprises ac[Arg-Gly-Asp-Phe-Lys] moiety (SEQ ID NO:9).

According to some embodiments of the invention, the anti-angiogenesisagent is Paclitaxel and the angiogenesis targeting moiety comprises twoc[Arg-Gly-Asp-Phe-Lys] moieties (SEQ ID NO:9).

According to some embodiments of the invention, the conjugate has thestructure:

wherein:

x is an integer having a value such that x/(x+y+w) multiplied by 100 isin the range of from 0.01 to 99.9;

y is an integer having a value such that y/(x+y+w) multiplied by 100 isin the range of from 0.01 to 99.9; and

w is an integer having a value such that w/(x+y+w) multiplied by 100 isin the range of from 0.01 to 99.9.

According to some embodiments of the invention, the conjugate has thestructure:

wherein:

-   -   x is an integer having a value such that x/(x+y+w) multiplied by        100 is in the range of from 70 to 99.9;    -   y is an integer having a value such that y/(x+y+w) multiplied by        100 is in the range of from 0.01 to 15; and    -   w is an integer having a value such that w/(x+y+w) multiplied by        100 is in the range of from 0.01 to 15.

According to some embodiments of the invention, the conjugate has ahydrodynamic diameter in the range of from 10 nm to 100 nm.

According to some embodiments of the invention, a load of thetherapeutically active agent in the polymer is greater than 1 mol %.

According to some embodiments of the invention, a load of theangiogenesis targeting moiety in the polymer is greater than 1 mol %.

According to some embodiments of the invention, the conjugate furthercomprising a labeling agent attached thereto.

According to an aspect of embodiments of the invention there is provideda pharmaceutical composition comprising, as an active ingredient, theconjugate as described herein and a pharmaceutically acceptable carrier.

According to some embodiments of the invention, the composition is beingpackaged in a packaging material and identified in print, in or on thepackaging material, for use in the treatment of a medical conditionassociated with angiogenesis.

According to some embodiments of the invention, the conjugate comprisesa labeling agent, the composition being packaged in a packaging materialand identified in print, in or on the packaging material, for use inmonitoring a medical condition associated with angiogenesis.

According to some embodiments of the invention, the condition isselected from a group consisting of atherosclerosis, cancer,hypertension, rheumatoid arthritis, diabetes and diabetes relatedcomplications.

According to an aspect of embodiments of the invention there is provideda method of treating a medical condition associated with angiogenesis ina subject in need thereof, the method comprising administering to thesubject a therapeutically effective amount of the conjugate as describedherein.

According to an aspect of embodiments of the invention there is provideda method of monitoring the level of angiogenesis within a body of apatient, the method comprising:

administering to the patient the conjugate having a labeling agent asdescribed herein attached thereto; and employing an imaging techniquefor monitoring a distribution of the conjugate within the body or withina portion thereof.

According to some embodiments, the condition is selected from the groupconsisting of atherosclerosis, cancer, hypertension, rheumatoidarthritis, diabetes and diabetes related complications.

According to an aspect of embodiments of the invention there is provideda use of the conjugate as described herein as a medicament.

According to an aspect of embodiments of the invention there is provideda use of the conjugate as described herein in the manufacture of amedicament for treating a medical condition associated withangiogenesis.

According to an aspect of embodiments of the invention there is provideda use of the conjugate having a labeling agent as described herein as adiagnostic agent.

According to an aspect of embodiments of the invention there is provideda use conjugate having a labeling agent as described herein in themanufacture of a diagnostic agent for monitoring a medical conditionassociated with angiogenesis.

According to an aspect of embodiments of the invention there is provideda process of synthesizing the conjugate as described herein, the processcomprising:

(a) co-polymerizing a plurality of monomeric units of the polymer, atleast one of the monomeric units terminating by a first reactive group,and at least one of the monomeric units terminating by a second reactivegroup, to thereby obtain a co-polymer that comprises a plurality ofbackbone units, at least one backbone unit having the first reactivegroup and at least one backbone unit having the second reactive group,the first reactive group being capable of reacting with the angiogenesistargeting moiety and the second reactive being capable of reacting withthe therapeutically active agent;

(b) reacting the co-polymer with the angiogenesis targeting moiety or aderivative thereof, via the first reactive group, to thereby obtain acopolymer having the angiogenesis targeting moiety attached to apolymeric backbone thereof; and

(c) further reacting the co-polymer with the therapeutically activeagent or a derivative thereof, via the second reactive group, to therebyobtain the co-polymer having the therapeutically active agent attachedto a polymeric backbone thereof, thereby obtaining the conjugate ofclaim 1.

According to some embodiments of the invention, (b) is performedsubsequent to, concomitant with or prior to (c).

According to some embodiments of the invention, at least one of themonomer units terminating by the first or the second reactive groupfurther comprises a linker linking the reactive group to the monomericunit.

Unless otherwise defined, all technical and/or scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which the invention pertains. Although methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of embodiments of the invention, exemplarymethods and/or materials are described below. In case of conflict, thepatent specification, including definitions, will control. In addition,the materials, methods, and examples are illustrative only and are notintended to be necessarily limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the invention are herein described, by way ofexample only, with reference to the accompanying drawings and images.With specific reference now to the drawings in detail, it is stressedthat the particulars shown are by way of example and for purposes ofillustrative discussion of embodiments of the invention. In this regard,the description taken with the drawings makes apparent to those skilledin the art how embodiments of the invention may be practiced.

In the drawings:

FIG. 1 presents the general formula of a polyglutamic acid basedconjugate, according to some embodiments of the invention, wherein apolyglutamic polymeric backbone is conjugated to a therapeuticallyactive agent through a degradable linker and to an angiogenesistargeting moiety. A is a —O— or —N— bond and R is a peptidic linkerwhich can be cleaved by enzymes such as Cathepsin B or MMP (i.e.Phe-Lys; SEQ ID NO: 12, Phe-Val-Gly-Leu-Ile-Gly; SEQ ID NO:13) or a pHlabile linker (i.e. ester or acetal). The average MW of the PGA polymerfrom which the polymeric backbone is derived is 152 grams/mole.

FIGS. 2A-G presents the 2-D chemical structure of Polyglutamic acid(PGA; FIG. 2A) Paclitaxel (PTX; FIG. 2B), a PGA-PTX conjugate, having amolecular weight average of 191.7 grams/mol (FIG. 2C), a PGA-c(RADfk)conjugate (SEQ ID NO: 14) having an average molecular weight of 181.59grams/mol (FIG. 3D); a PGA-E-c(RGDfk)₂ conjugate (SEQ ID NO: 15; FIG.2E); a PGA-PTX−c(RGDfk) conjugate (SEQ ID NO: 16; FIG. 2F) and aPGA-c(RGDfk) conjugate (SEQ ID NO: 17; FIG. 2G).

FIGS. 3A-B present the 2-D chemical structure of the PGA-PTX−E-c(RGDfk)₂conjugate (SEQ ID NO: 18) according to some embodiments of theinvention, in which the average molecular weight of the PGA polymer fromwhich the polymeric backbone is derived is 256.53 grams/mol, (FIG. 3A)and of a PGA-PTX−c(RADfk) conjugate (SEQ ID NO: 19) according to someembodiments of the invention in which the molecular weight of the PGApolymer from which the polymeric backbone is derived is 221.54 grams/mol(FIG. 3B).

FIGS. 4A-D present a scheme illustrating an optional synthetic pathwayfor generating the anti-angiogenesis agent TNP-470 having attachedthereto a NH₂(CH₂)₂NH₂ moiety (FIG. 4A), as well as the 2-D chemicalstructures of a PGA-(TNP-470) conjugate (FIG. 4B),PGA-(TNP-470)-c(RADfk) conjugate (SEQ ID NO: 20; FIG. 4C) andPGA-(TNP-470)-E-[c(RGDfk)₂] conjugate (SEQ ID NO: 21), according to someembodiments of the present invention (FIG. 4D).

FIG. 5 presents the 2-D chemical structure of a polyethylenglycolpolymer having conjugated thereto PTX and c(RGDfk)₂[PEG-PTX−E-[c(RGDfk)₂, according to some embodiments of the presentinvention (SEQ ID NO: 22).

FIG. 6 presents a scheme illustrating the synthesis of an HPMAcopolymer-E-[c(RGDfk)₂]-Paclitaxel conjugate (SEQ ID NO:23) according tosome embodiments of the present invention.

FIG. 7 presents a scheme illustrating the synthesis of a polyglutamicacid based polymer conjugate [PGA-PTX−E-c(RGDfk)₂] (SEQ ID NO: 18), aconjugate according to some embodiments of the present invention.

FIG. 8 presents a scheme illustrating the synthesis of a polyglutamicacid polymer and c(RGDfk)₂ conjugate [PGA-E-c(RGDfk)₂] (SEQ ID NO: 15).

FIGS. 9A-C present bar diagrams of the hydrodynamic diameters of twosynthesized conjugates [PGA-PTX−E-c(RGDfk)₂] (SEQ ID NO: 18; FIGS. 9Aand 9B) and the synthesized conjugate [PGA-PTX−c(RGDfk)] (SEQ ID NO:16FIG. 9C), all being conjugates according to some embodiments of thepresent invention. The hydrodynamic diameter of the conjugates wasassessed using laser light scattering microscopy with the NanoparticleTracking Analysis (NTA) technology. The mean hydrodynamic diameter ofthe conjugate [PGA-PTX−E-c(RGDfk)₂] (SEQ ID NO: 18) with PTX loading of5.5 mol % and -E-c(RGDfk)₂ loading of 3.9 mol % is shown in FIG. 9A. Themean hydrodynamic diameter of the conjugate [PGA-PTX−E-c(RGDfk)₂] (SEQID NO: 18) with PTX loading of 2.6 mol % and -E-c(RGDfk)₂ loading of 5mol % is shown in FIG. 9B. The mean hydrodynamic diameter of theconjugate [PGA-PTX−c(RGDfk)] (SEQ ID NO:16) with PTX loading of 2.1 mol% and with -c(RGDfk) loading of 5 mol % is shown in FIG. 9C.

FIGS. 10A-B present paclitaxel release profile kinetics from variousPGA-based conjugates in the presence of Cathepsin B or hydrolyticconditions. Presented in FIG. 10A are comparative plots of thepercentage of Paclitaxel release from a conjugate of PGA and PTX(PGA-PTX; filled diamonds), a PGA-PTX−c(RADfk) conjugate (SEQ ID NO: 19;filled squares), a PGA-PTX−E-[c(RGDfk)₂] conjugate (SEQ ID NO:18);filled triangles), and a PGA-PTX-[c(RGDfk)] conjugate (SEQ ID NO:16;crosses), which were incubated with cathepsin B, as a function of time.Presented in FIG. 10B are comparative plots of the percentage ofPaclitaxel release from a PGA-PTX−E-[c(RGDfk)₂] conjugate (SEQ ID NO:18;having a loading of 2.6% mol PTX and 5 mol % E-[c(RGDfk)₂], (filledtriangles), and a PGA-PTX−E-[c(RGDfk)₂] conjugate (SEQ ID NO:18) havinga loading of 5.5% mol PTX and 3.9 mol % E-[c(RGDfk)₂], (filleddiamonds), which were incubated with cathepsin B, as a function of time.

FIGS. 11A-C present data showing the cell expression of αvβ₃ integrinand its interaction with conjugates according to embodiments of theinvention. HUVEC, U87 human glioblastoma cells and PANC02 murinepancreatic tumor cells were subjected to immunostaining with anti-αvβ₃followed by a fluorescently labeled secondary antibody and scanned forαvβ₃ presence using FACS (see FIG. 11A). Serving as control were cellsnot incubated with any antibody. Analysis of the results showed thatonly HUVEC, and U87 cells but not PANC02 cells expressed the αvβ₃integrin. The florescence probe Oregon Green-cadaverine (OG), wasconjugated to PGA-c(RADfk) (SEQ ID NO: 14) and to PGA-E-[c(RGDfk)₂](SEQID NO: 15) to result in a (PGA-c(RADfk)-OG (SEQ ID NO: 24) orPGA-E-[c(RGDfk)_(2])-OG (SEQ ID NO:25)) and their adhesion to αvβ₃ wasassessed by incubation with human umbilical vein endothelial cells(HUVEC) followed by determination of the change in fluorescence usingthe ImageStream 100 imaging flow cytometer (Merkel Technologies Ltd.)(see, FIG. 11B). FIG. 11C presents images of the cells following 15minutes of incubation with either PGA-c(RADfk)-OG (SEQ ID NO: 24; rightpicture) or PGA-E-[c(RGDfk)₂]-OG (SEQ ID NO:25; left picture) showingthe higher uptake of conjugate containing the [c(RGDfk)₂] moiety (SEQ IDNO: 26) by the cells as compared to the inactive, RAD (SEQ ID NO: 27)containing, conjugate.

FIGS. 12A-C present comparative plots demonstrating that Paclitaxelretains its anti-angiogenic effect on the proliferation of HUVEC (FIG.12A), U87 human glioblastoma cells (FIG. 12B) and PANC02 murinepancreatic tumor cells (FIG. 12C) when conjugates to the PGA-c(RGDfk)₂polymer (SEQ ID NO:15), according to some embodiments of the invention.Results are presented as percents of cell growth (out of the controlgroup) as a function of Paclitaxel concentration, for polyglutamic acidpolymer alone (PGA, orange full squares); Paclitaxel alone (PTX, lightblue empty squares), polyglutamic acid polymer conjugated to Paclitaxel(PGA-PTX; purple filled squares), Polyglutamic acid polymer conjugatedto Paclitaxel and to the inactive cyclic peptide RAD (PGA-PTX−c(RADfk);SEQ ID NO: 19; dark blue empty circles); the free inactive cyclicpeptide RAD (c(RADfk); SEQ ID NO: 28; pink filled diamonds);Polyglutamic acid polymer conjugated to a bis-cyclic RGD-containingpeptide (PGA-E-[c(RGDfk)_(2]); SEQ ID NO: 15; green filled triangles);free Paclitaxel+free inactive peptide RAD (PTX+c(RADfk) having SEQ IDNO: 28; blue empty diamonds); Polyglutamic acid polymer conjugated toPaclitaxel and to bis-cyclic RGD peptide, a conjugate according to someembodiments of the present invention (PGA-PTX−E-[c(RGDfk)₂]; SEQ ID NO:18; green filled circles); free bis-cyclic RGD peptide (E-[c(RGDfk)₂];SEQ ID NO: 2; red filled triangles); Polyglutamic acid polymerconjugated to inactive cyclic peptide RAD (PGA-c(RADfk); SEQ ID NO: 14;dark blue filled diamonds) and Paclitaxel conjugated to the bis-cyclicRGD-containing peptide (PTX−E-[c(RGDfk)₂]; SEQ ID NO: 29; green emptyfilled triangles); Solid and dashed lines represent the proliferation ofcells in the presence (solid line) or absence (dashed line) of growthfactors. Data represent mean±SD. The PGA-PTX−E-[c(RGDfk)₂] conjugate(SEQ ID NO: 18) used for the present experiments was the first conjugatesynthesized (i.e. having a 5.5 mol % PTX and 3.9 mol % E-[c(RGDfk)₂]loading).

FIGS. 13A-B present comparative plots demonstrating theanti-proliferative effect on HUVEC of a PGA-PTX−E-[c(RGDfk)₂] conjugate(SEQ ID NO: 18) according to some embodiments of the invention, having a5 mol % E-[c(RGDfk)₂] and 2.6 mol % PTX loading (FIG. 13A) and theanti-proliferative effect of the PGA-PTX−c(RGDfk) conjugate (SEQ IDNO:16; FIG. 13B). Results are presented as percents of cell growth (outof the control group) as a function of Paclitaxel concentration, forpolyglutamic acid polymer alone (PGA, orange full squares); Paclitaxelalone (PTX, light blue empty squares), polyglutamic acid polymerconjugated to Paclitaxel (PGA-PTX; purple filled squares), polyglutamicacid polymer conjugated to Paclitaxel and to the inactive cyclic peptidec(RADfk) (PGA-PTX−c(RADfk); SEQ ID NO: 19; dark blue empty circles); theinactive cyclic peptide c(RADfk) (c(RADfk); SEQ ID NO:28; pink filleddiamonds); polyglutamic acid polymer conjugated to bis-cyclic RGDpeptide (PGA-RGD; SEQ ID NO:17; green filled triangles) freePaclitaxel+free inactive peptide c(RADfk) (PTX+c(RADfk) having SEQ IDNO:28; blue empty diamonds); polyglutamic acid polymer conjugated toPaclitaxel and to bis-cyclic RGD peptide (in FIG. 13A) or to themonocyclic RGD (in FIG. 13B), (PGA-PTX-RGD; SEQ ID NO: 16; green filledcircles); bis-cyclic RGD peptide alone (c(RGDfk)₂; SEQ ID NO: 26; redfilled triangles); polyglutamic acid polymer conjugated to inactivecyclic peptide c(RADfk) (PGA-c(RADfk); SEQ ID NO: 14; dark blue filleddiamonds) and Paclitaxel conjugated to the bis-cyclic RGD peptide(PTX−E-c(RGDfk)₂; SEQ ID NO: 29; green empty filled triangles); Solidand dashed lines represent the proliferation of cells in the presence(solid line) or absence (dashed line) of growth factors. Data representmean±SD.

FIG. 14 present a bar graph showing the effect of PGA-PTX−E-[c(RGDfk)₂](SEQ ID NO: 18) a conjugate according to some embodiments of the presentinvention, on the ability of HUVEC to migrate towards vascularendothelial growth factor (VEGF) chemoattractant and the ability to formcapillary-like tube structures. Presented are the percentages ofinhibition of HUVEC capillary-like tube structures by polyglutamic acidpolymer alone (PGA); Paclitaxel alone (PTX); the inactive cyclic peptidec(RADfk) (c(RADfk); SEQ ID NO:28); bis-cyclic RGD peptide alone(E-[c(RGDfk)_(2]); SEQ ID NO:2); polyglutamic acid polymer conjugated toPaclitaxel and to the inactive cyclic peptide c(RADfk)(PGA-PTX−c(RADfk)); polyglutamic acid polymer conjugated to bis-cyclicRGD peptide (PGA-E-[c(RGDfk)_(2]); SEQ ID NO:15); polyglutamic acidconjugated to Paclitaxel (PGA-PTX); a combination of free Paclitaxeltogether with free inactive cyclic peptide c(RADfk) (PTX+c(RADfk) havingSEQ ID NO:28); a combination of free Paclitaxel together with free thebis-cyclic RGD peptide (PTX+E-[c(RGDfk)₂] having SEQ ID NO:26);polyglutamic acid polymer conjugated to inactive cyclic peptide c(RADfk)(PGA-c(RADfk); SEQ ID NO:14) and polyglutamic acid polymer conjugated toPaclitaxel and to bis-cyclic RGD peptide, a conjugate according to someembodiments of the present invention (PGA-PTX−E-[c(RGDfk)_(2]); SEQ IDNO:18) compared with non-treated cells (only with VEGF). Also shown isthe percent of migration of cells not exposed to VEGF (No VEGF). Datarepresent mean±SD.

FIG. 15 presents a bar graph demonstrating thatPGA-Paclitaxel-E-[c(RGDfk)₂] and PGA-Paclitaxel-[cRGDfk], (SEQ ID NOs:18 and 16 respectively) both conjugates according to some embodiments ofthe invention, blocked the adhesion of HUVEC to fibrinogen coatedplates. The percentage of HUVEC attachment after treatments wasquanified and normalized to the percent of attachment of control cells(i.e., not incubated with any compound; marked as Cells only). Theattached cells were fixed and dyed. Shown are three experimentsperformed: the first using the conjugate PGA-Paclitaxel-E-[c(RGDfk)₂](SEQ ID NO: 18) having a 5.5 mol % PTX and 3.9 mol % of E-[c(RGDfk)₂loading (dark gray); the second using the conjugatePGA-Paclitaxel-E-[c(RGDfk)₂] (SEQ ID NO:18) having a 2.6 mol % PTX and 5mol % of E-[c(RGDfk)₂ loading (light gray); and a third using theconjugate PGA-Paclitaxel-c(RGDfk) (SEQ ID NO:16; having a 2.1 mol % PTXand 5 mol % of c(RGDfk) loading (white). The cells were incubated withthe following tested compounds: the inactive cyclic peptide c(RADfk)(c(RADfk); SEQ ID NO:28); monocyclic RGD peptide alone (E-[c(RGDfk)];SEQ ID NO:9); polyglutamic acid polymer alone (PGA); polyglutamic acidconjugated to Paclitaxel (PGA-PTX); polyglutamic acid polymer conjugatedto inactive cyclic peptide c(RADfk) (PGA-c(RADfk); SEQ ID NO:14);polyglutamic acid polymer conjugated to bis-cyclic RGD peptide(PGA-E-[c(RGDfk)_(x)] wherein in the first two experiments x=2 and inthe third experiment x=1; having ID SEQs of 15 and 17 when X=1 and 2respectively); Paclitaxel alone (PTX); a combination of free Paclitaxeltogether with free inactive cyclic peptide c(RADfk) (PTX+c(RADfk) havingSEQ ID NO:28); a combination of free Paclitaxel together with free thebis-cyclic RGD peptide (PTX+E-[c(RGDfk)_(x)] wherein in the first twoexperiments x=2 (SEQ ID NO:2) and in the third experiment x=1 (SEQ IDNO:9); polyglutamic acid polymer conjugated to Paclitaxel and to theinactive cyclic peptide c(RADfk) (PGA-PTX−c(RADfk); SEQ ID NO:19); andpolyglutamic acid polymer conjugated to Paclitaxel and to bis-cyclic RGDpeptide (PGA-PTX-[c(RGDfk)_(x)] wherein in the first two experiments x=2and in the third experiment x=1 having ID SEQs of 18 and 16 when X=1 and2 respectively). Whenever x=2, the c(RGDfk) moiety further includes aglutamate residue (-E-) to which the two cyclic RGDfk moieties areconnected. Shown as control are cells not incubated with any compound(Cells only). Also shown are control cells seeded on plates withoutfibrinogen coating (No fibrinogen). The quantification was performedusing Nikon TE2000E inverted microscope and NIH image software.*Treatment with c(RGDfk)₂ (SEQ ID NO:9; was at 20 μM concentration,while Paclitaxel was at 5 nM because Paclitaxel at a higher dose istoxic to the cells. Data represent mean±SD.

FIGS. 16A-B present images (FIG. 16A) and a bar graph (FIG. 16B)demonstrating that the conjugate PGA-Paclitaxel-c(RGDfk)₂ (SEQ ID NO:18) inhibited capillary-like tube formation of HUVEC. HUVEC (5×10⁴cells/100 μl) were challenged with polyglutamic acid polymer alone(PGA); Paclitaxel alone (PTX); bis-cyclic RGD peptide alone(E-[c(RGDfk)_(2]); SEQ ID NO:2); the inactive cyclic peptide c(RADfk)(c(RADfk); SEQ ID NO:28); Polyglutamic acid conjugated to Paclitaxel(PGA-PTX); Polyglutamic acid polymer conjugated to bis-cyclic RGDpeptide (PGA-E-[c(RGDfk)_(2]); SEQ ID NO:15); Polyglutamic acid polymerconjugated to inactive cyclic peptide c(RADfk) (PGA-c(RADfk); SEQ IDNO:14); a combination of free Paclitaxel together with free thebis-cyclic RGD peptide (PTX+E-[c(RGDfk)₂] having SEQ ID NO:2); acombination of free Paclitaxel together with free inactive cyclicpeptide c(RADfk) (PTX+c(RADfk) having SEQ ID NO:28); Polyglutamic acidpolymer conjugated to Paclitaxel and to the inactive cyclic peptidec(RADfk) (PGA-PTX−c(RADfk); SEQ ID NO:19) and Polyglutamic acid polymerconjugated to Paclitaxel and to bis-cyclic RGD peptide(PGA-PTX-[c(RGDfk)_(2]); SEQ ID NO:18). The cells were then stained andthe percentages of inhibition of HUVEC capillary-like tube structures bythe different compounds were determined. Quantification was performedusing Nikon TE2000E inverted microscope and NIH image software. Datarepresent mean±SD.

FIGS. 17A-B present data showing the selective accumulation of theconjugates in tumor tissues in vivo. The florescence probe OregonGreen-cadaverine (OG), was conjugated to PGA, PGA-E-[c(RGDfk)₂] (SEQ IDNO:15) and PGA-c(RADfk) (SEQ ID NO:14). SCID male were inoculated s.c.with 2×10⁶ mCherry-labeled U87 human osteosarcoma or with 5×10⁶mCherry-labeled MG-63 human osteosarcoma and injected i.v. withPGA-E-[c(RGDfk)₂]-OG (SEQ ID NO:25; 50 μM-RGD) or PGA-c(RADfk)-OG (SEQID NO: 24; 50 μM-RGD-equivalent dose) or PGA as control (n=3mice/group). One hour after injection, tumors were removed, dissected tothin slices and examined under Zeiss Meta LSM 510 confocal imagingsystem. Shown in FIG. 17A are fluorescent images of tumor slices fromthe treated mice showing that only PGA-E-[c(RGDfk)₂] (SEQ ID NO: 15) wasable to accumulate in the tumor tissue. FIG. 17B presents comparativeplots of the accumulation of PGA-PTX−E-[c(RGDfk)₂]-OG (SEQ ID NO:25),PGA-PTX−c(RADfk)-OG (SEQ ID NO:24) and PGA-PTX-OG, as detected via FACS,in the mCherry-labeled-MG-63 cells from homogenized tumors of thetreated mice. The results show the PGA-PTX−E-[c(RGDfk)₂]-OG (SEQ ID NO:25) preferential accumulation compared with PGA-PTX−c(RADfk)-OG (SEQ IDNO:24) and PGA-PTX-OG.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

The present invention, in some embodiments thereof, relates to novelchemical conjugates and to uses thereof in therapy and diagnosis and,more particularly, but not exclusively, to novel conjugates of polymershaving attached thereto an angiogenesis targeting moiety and ananti-angiogenesis agent and to uses thereof in monitoring and treatingmedical conditions associated with angiogenesis.

The principles and operation of the conjugates, compositions, use,methods and processes according to the invention may be betterunderstood with reference to the drawings and accompanying descriptions.

Before explaining at least one embodiment of the invention in detail, itis to be understood that the invention is not limited in its applicationto the details set forth in the following description or exemplified bythe Examples. The invention is capable of other embodiments or of beingpracticed or carried out in various ways. Also, it is to be understoodthat the phraseology and terminology employed herein is for the purposeof description and should not be regarded as limiting.

The term “angiogenesis” describes a biological process that involves thesprouting of new blood vessels from pre-existing ones and plays acrucial role in disease development and progression [Folkman J. N Engl JMed 1995, 333:1757-1763]. Angiogenesis is a complex process in whichendothelial cells serve as a building block for blood vessel expansion.It is regulated through a fine balance between pro-angiogenic andanti-angiogenic molecules.

Pathological angiogenesis has been demonstrated in several diseases,including cancer, hypertension, rheumatoid arthritis, and diabeticretinopathy. Tumor growth and metastasis are particularly dependent onthe degree of angiogenesis.

Inhibition of further vascular expansion has therefore been the focus ofactive research for cancer therapy. Many drugs have been developed,which target different steps in this multi-step tumor angiogenesisprocess. However, most of these drugs were shown to be cytostatic ratherthan cytotoxic and thus do not cause a substantial reduction of tumorvolume during the first stage of treatment.

In a search for novel agents for treating medical conditions associatedwith angiogenesis, the present inventors have devised and successfullyprepared and practiced novel conjugates of a biocompatible polymer,which has a therapeutically active agent that is useful as ananti-cancer agent and/or an anti-angiogenesis agent and at least oneArg-Gly-Asp (RGD)-containing moiety (SEQ ID NO: 1) as an angiogenesistargeting moiety attached thereto.

As demonstrated in the Examples section that follows, these novelconjugates were shown to inhibit angiogenesis and angiogenesis relatedprocesses, and thus were shown to inhibit endothelial cellproliferation, migration ability of cells to form capillary-like tubestructures and adhesion onto fibrinogen coated plates (see, FIGS.12-16). Furthermore, in vivo experiments showed enhanced accumulation ofan exemplary conjugate according to some embodiments of the presentinvention, denoted as PGA-PTX−E-[c(RGDfk)₂] (SEQ ID NO:18), inosteosarcoma tumor cells in mice (FIG. 17).

These conjugates can therefore be beneficially used for the treatment ofmedical conditions characterized by excessive angiogenesis.

Thus, according to one aspect of embodiments of the invention there isprovided a polymeric conjugate comprising a polymeric backbone havingattached thereto a therapeutically active agent and an angiogenesistargeting moiety, the angiogenesis targeting moiety comprising a leastone Arg-Gly-Asp (RGD)-containing moiety (SEQ ID NO:1) and thetherapeutically active agent being an anti-angiogenesis agent and/or ananti-cancer agent.

In some embodiments of the invention, the conjugates described hereincomprise a polymeric backbone comprised of a plurality of backboneunits, whereby a portion of these backbone units have thetherapeutically active agent attached thereto and another portion ofthese backbone units have the angiogenesis targeting moiety attachedthereto. Those backbone units within the polymeric backbone that are notlinked to another moiety are referred to herein as “free” or“non-functionalized” backbone units.

Since the polymeric backbone in the conjugates described herein iscomposed of some backbone units that have the therapeutically activeagent attached thereto, some backbone units that have the targetingmoiety attached thereto, and optionally some free backbone units, theseconjugates represent co-polymers.

The phrase “therapeutically active agent” describes a compound whichexhibits a beneficial pharmacological effect when administered to asubject and hence can be used in the treatment of a condition thatbenefits from this pharmacological effect.

The term “subject” (alternatively referred to herein as “patient”) asused herein refers to an animal, preferably a mammal, most preferably ahuman, who has been the object of treatment, observation or experiment.

The phrase “anti-cancer agent”, as used herein, describes anytherapeutic agent that directly or indirectly kills cancer cells ordirectly or indirectly inhibits, stops or reduces the proliferation ofcancer cells. Anti-cancer agents include those that result in cell deathand those that inhibit cell growth, proliferation and/ordifferentiation. In some embodiments, the anti-cancer agent isselectively toxic against certain types of cancer cells but does notaffect or is less effective against normal cells. In some embodiments,the anti-cancer agent is a cytotoxic agent.

The phrase “cytotoxic agent”, as used herein, describes a compound thatmediates cell death. Cell death mediation can be exhibited by amechanism such as, but not limited to, apoptosis, inhibition ofmetabolism or DNA synthesis, interference with cytoskeletalorganization, destabilization or chemical modification of DNA, etc. Asused herein, the phrase “cytotoxic agent” encompasses any suitablechemotherapeutic agent, including small organic molecules, peptides,oligonucleotides and the like as well as radiotherapeutic agents suchas, for example, radioactive iodine ¹³¹I and beta particle emitter ⁹⁰Y.The agent may act, for example, as an anti-proliferative agent or as apro-apoptotic agent, which induces apoptosis.

Exemplary cytotoxic agents include, without limitation, AnthracyclineAntibiotics such as Doxorubicin and Daunorubicin, Taxanes such asTaxol™, Docetaxel, Vinca alkaloids as Vincristine and Vinblastine,5-Fluorouracil (5 FU), Leucovorin, Irinotecan, Idarubicin, Mitomycin C,Oxaliplatin, Raltitrexed, Tamoxifen and Cisplatin, Carboplatin,Methotrexate, Actinomycin D, Mitoxantrone or Blenoxane or Mithramycin.

The agent can also be a member of the Bio-Reductive drugs that areactivated under hypoxic cellular conditions.

Some anti-cancer agents act as angiogenesis inhibitors, as discussedhereinabove.

The phrase “anti-angiogenesis agent”, which is also referred to hereininterchangeably as “anti-angiogenic agent” or “angiogenesis inhibitor”,describes an agent having the ability to (a) inhibit endothelial cellproliferation or migration, (b) kill proliferating endothelial cells,and/or (c) inhibit the formation of new blood vessels in a tissue.

As discussed hereinabove, some anti-angiogenesis agents are useful inthe treatment of cancer and hence can also be referred to as anti-canceragents.

In some embodiments the anti-angiogenesis agent is Paclitaxel.

The chemical structure of Paclitaxel is shown in FIG. 2B. Themicrotubule-interfering agent Paclitaxel is a drug commonly used for thetreatment of advanced metastatic breast cancer. However, it isneurotoxic, it causes hematological toxicity and many breast tumorsdevelop resistance thereto. It has been recently shown that Paclitaxelat ultra low doses inhibits angiogenesis. However, Paclitaxel is poorlysoluble in aqueous solutions and the excipients Cremophor EL or ethanolused today to solubilize its commercial form, cause hypersensitivityreactions.

As demonstrated in the Examples section which follows, a conjugatecomprising Paclitaxel, according to some embodiments of the invention,at a concentration in which Paclitaxel has been known to exhibitanti-angiogenesis activity, has been tested for its anti-angiogenesisactivity. Specifically, the conjugate being a Polyglutamic acidco-polymer in which two RGD-containing cyclic peptides and Paclitaxelare conjugated to the polymeric backbone (PGA-E-c(RGDfk)₂-PTX; SEQ IDNO:18) has been shown to exhibit anti-angiogenesis activity, namelyinhibit endothelial cell proliferation, migration, ability of cells toform capillary-like tube structures and adhesion onto fibrinogen coatedplates (see, FIGS. 12-16). Another conjugate being a Polyglutamic acidpolymer linked to one RGD-containing cyclic peptide and to Paclitaxel(PGA-c(RGDfk)-PTX; SEQ ID NO:16) has been also shown to exhibitanti-angiogenesis activity (see, FIGS. 13B and 15). These resultsdemonstrate the ability of the conjugates described herein, to inhibitangiogenesis and therefore to serve as potent anti-angiogenesis agents.

In some embodiments the anti-angiogenesis agent is TNP-470.

TNP-470 is a low molecular weight synthetic analogue of fumagillin,which is capable of selectively inhibiting endothelial growth in vitro.In clinical trials, this drug was found to slow tumor growth in manypatients with metastatic cancer and exhibited a promising efficacy whenused in combination with conventional chemotherapy. However, at thedoses required for tumor regression, many TNP-470-treated patientsexperienced neurotoxicity. Due to its dose-limiting neurotoxicity, nofurther clinical studies were conducted for using TNP-470 per se. Arepresentative chemical structure of a TNP-470 containing conjugate(PGA-TNP-470-[c(RGDfk)₂]; SEQ ID NO:21), according to some embodimentsof the present invention, is presented in FIG. 4D.

Other anti-angiogenesis agents that are suitable for use in the contextof embodiments of the invention include, but are not limited to,paclitaxel, 2-methoxyestradiol, prinomastat, batimastat, BAY 12-9566,carboxyamidotriazole, CC-1088, dextromethorphan acetic acid,dimethylxanthenone acetic acid, endostatin, IM-862, marimastat, a matrixmetalloproteinase, penicillamine, PTK787/ZK 222584, RPI.4610, squalaminelactate, SU5416, thalidomide, combretastatin, tamoxifen, COL-3,neovastat, BMS-275291, SU6668, anti-VEGF antibody, Medi-522 (VitaxinII), CAI, Interleukin-12, IM862, Amilloride, Angiostatin®Protein,Angiostatin K1-3, Angiostatin K1-5, Captopril,DL-alpha-Difluoromethylornithine, DL-alpha-Difluoromethylornithine HCl,His-Tag® Endostatin™Protein, Endostar™, Fumagillin, Herbimycin A,4-Hydroxyphenylretinamide, Juglone, Laminin, Laminin Hexapeptide,Laminin Pentapeptide, Lavendustin A, Medroxyprogesterone,Medroxyprogesterone Acetate, Minocycline, Minocycline HCl, PlacentalRibonuclease Inhibitor, Suramin, Sodium Salt Suramin, Human PlateletThrombospondin, Neutrophil Granulocyte, monoclonal antibodies directedagainst specific proangiogenic factors and/or their receptors (e.g.Avastin, Erbitux, Vectibix, Herceptin); small molecule tyrosine kinaseinhibitors of multiple pro-angiogenic growth factor receptors (e.g.Tarceva, Nexavar, Sutent, Iressa); inhibitors of mTOR (mammalian targetof rapamycin) (e.g. Torisel); interferon alpha, beta and gamma; IL-12;matrix metalloproteinases (MMP) inhibitors (e.g. COL3, Marimastat,Batimastat); EMD121974 (Cilengitide); ZD6474, SU11248, Vitaxin;Squalamin; COX-2 inhibitors; PDGFR inhibitors (e.g., Gleevec); NM3 and2-ME2.

In some embodiments, the anti-angiogenesis agent is selected from thegroup consisting of Paclitaxel, monoclonal antibodies directed againstspecific proangiogenic factors and/or their receptors (e.g. Avastin,Erbitux, Vectibix, Herceptin); small molecule tyrosine kinase inhibitorsof multiple proangiogenic growth factor receptors (e.g. Tarceva,Nexavar, Sutent, Iressa); inhibitors of mTOR (mammalian target ofrapamycin) (e.g. Torisel); interferon alpha, beta and gamma; IL-12;matrix metalloproteinases (MMP) inhibitors (e.g. COL3, Marimastat,Batimastat); EMD121974 (Cilengitide); Vitaxin; Squalamin; COX-2inhibitors; PDGFR inhibitors (e.g., Gleevec); NM3; 2-ME2 andBisphosphonates (e.g., Zoledronate).

As used herein, the term “COX-2 inhibitor” refers to a non-steroidaldrug that relatively inhibits the enzyme COX-2 in preference to COX-1.Preferred examples of COX-2 inhibitors include, but are no limited to,celecoxib, parecoxib, rofecoxib, valdecoxib, meloxicam, and etoricoxib.

The phrase “angiogenesis targeting moiety” describes a chemical moietythat can bind to a location in a mammal in which neovascularization,such as neovascularization of tumor cells, occurs. The phrase“neovascularization” is meant to encompass two unique processes:vasculogenesis, the de novo assembly of blood vessels, and angiogenesis,the formation of new capillary sprouts from pre-existing vessels.

The angiogenesis targeting moiety described herein is derived fromcompounds that can selectively bind to a location in a mammal in whichneovascularization occurs and hence may serve to deliver the conjugatedescribed herein to the desired location.

In some embodiments the targeting moiety is capable of binding to anangiogenesis-associated integrin. In some embodiments, the targetingmoiety targets the α_(v)β₃ integrin receptor.

Integrins are a class of receptors involved in the mechanism of celladhesion. The integrins are heterodimeric transmembrane glycoproteinsthat compose a diverse family of 19α and eight β subunits. An integrinwith a well-characterized involvement in angiogenesis and tumorinvasiveness is α_(v)β₃ [Stromblad and Cheresh, Chem Biol 1996;3:881-885]. The α_(v)β₃ integrin is overexpressed on proliferatingendothelial cells such as those present in growing tumors, as well as onsome tumor cells of various origins. The RGD sequence (SEQ ID NO:1)represent the minimal amino acid domain, in several extracellular matrixproteins, which has been demonstrated to be the binding site of thetransmembrane integrins proteins family [Bazzoni et al. 1999, CurrentOpinion in Cell Biology; (11) pp. 573-581].

Accordingly, in some embodiments, the angiogenesis targeting moietycomprises a least one Arg-Gly-Asp (RGD) moiety (SEQ ID NO:1), or apeptidomimetic thereof, and can optionally further include other aminoacids, amino acid derivatives, or other chemical groups (e.g., alkylenechains).

In some embodiments, the RGD-containing moiety (SEQ ID NO:1) is anoligopeptide. The oligopeptide can be a cyclic oligopeptide (including,for example, monocyclic, bicyclic and tricyclic oligopeptides) or alinear oligopeptide, and can include, in addition to the Arg-Gly-Aspamino acid sequence (SEQ ID NO:1), from 1 to 10 amino acids.

It has been further found that the substrate specificity ofRGD-containing moieties (SEQ ID NO:1) results from the differentconformations of the RGD sequence in different matrix proteins.

In an embodiment, the oligopeptide is a cyclic peptide beingc[Arg-Gly-Asp-Phe-Lys] (SEQ ID NO:9).

In some embodiments, the angiogenesis targeting moiety comprises two ormore Arg-Gly-Asp-containing moieties (SEQ ID NO:1), wherein the moietiescan be the same or different.

Exemplary Arg-Gly-Asp-containing moieties (SEQ ID NO:1) that aresuitable for use in the context of embodiments of the invention include,but are not limited to c(RGDfk) (SEQ ID NO:9), RGD4C (SEQ ID NO:5), andother RGD-containing cyclic peptides such as those described in Haubneret al. [J. Am. Chem. Soc. 1996, 118, 7881-7891] and Capello, et al. [J.Nucl. Med. 2004, 45(10), 1716-20] and in WO 97/06791 and U.S. Pat. No.5,773,412. Exemplary effective RGD cyclic peptides are the Arg-Gly-Asp(RGD) cyclic pentapeptides in which two amino acids such as D-tyrosineand lysine were added to the RGD and the pentapeptide was transformedinto cyclic pentapeptide.

In some embodiments, the RGD-containing moiety can comprise two or more-Arg-Gly-Asp-moieties (SEQ ID NO:1), being either linked to one anotheror being spaced by one or more amino acids or any other spacer, asdefined herein.

As demonstrated in the Examples section that follows, an RGD-containingmoiety c(RGDfk)₂ conjugated to a PGA polymeric backbone (SEQ ID NO:15)bound to a greater extent to cells expressing the α_(v)β₃ integrin ascompared to a PGA conjugate of the inactive RAD moiety or PGA alone (SEQID NO:14) (see, FIGS. 11B and 11C), thereby demonstrating that the RGDmoiety plays a key role in the interaction and subsequentinternalizations of the conjugates into the cells.

In some embodiments, the anti-angiogenesis agent is Paclitaxel and theangiogenesis targeting moiety comprises a cyclic oligopeptide beingc[Arg-Gly-Asp-Phe-Lys] (SEQ ID NO:9).

In some embodiments the anti-angiogenesis agent is Paclitaxel and theangiogenesis targeting moiety comprises two cyclic oligopeptides eachbeing c[Arg-Gly-Asp-Phe-Lys] (SEQ ID NO:9). Such a conjugate is referredto herein as a conjugate that contains a bis-cyclic RGD-containingmoiety.

Herein, the phrases “loading onto the polymer”, or simply “load”, areused to describe the amount of an agent that is attached to thepolymeric backbone of the conjugates described herein, and isrepresented herein by the mol % of this agent in the conjugate, asdefined hereinafter.

As used herein, the term “mol %” describes the number of moles of anattached moiety per 1 mol of the polymeric conjugate, multiplied by 100.

Thus, for example, a 1 mol % load of an angiogenesis targeting moietydescribes a polymeric conjugate composed of 100 backbone units, whereby1 backbone unit has a targeting moiety attached thereto and the other 99backbone units are either free or have other agents attached thereto.

The optimal degree of loading of the therapeutically active agent andangiogenesis targeting moiety for a given conjugate and a given use isdetermined empirically based on the desired properties of the conjugate(e.g., water solubility, therapeutic efficacy, pharmacokineticproperties, toxicity and dosage requirements), and optionally on theamount of the conjugated moiety that can be attached to a polymericbackbone in a synthetic pathway of choice.

The % loading can be measured by methods well known by those skilled inthe art, some of which are described hereinbelow under the Materials andMethods of the Examples section that follows.

In some embodiments, the loading of the therapeutically active agent inthe polymer is greater than 1 mol %.

In some embodiments, the loading of the therapeutically active agent inthe conjugate ranges from 1 mol % to 99 mol %, from 1 mol % to 50 mol %,from 1 mol % to 20 mol %, from 1 mol % to 10 mol 5, or from 1 mol % to 5mol %.

In some embodiments the loading of the angiogenesis targeting moiety inthe polymer is greater than 1 mol %.

In some embodiments, the loading of the angiogenesis targeting moiety inthe conjugate ranges from 1 mol % to 99 mol %, from 1 mol % to 50 mol %,from 1 mol % to 20 mol %, from 1 mol % to 10 mol %, or from 1 mol % to 5mol %.

As exemplified in the Examples section that follows, conjugates having adifferent % loading of the therapeutically active agent and angiogenesistargeting moiety were synthesized (see, Table 1) and theiranti-angiogenesis activity was determined. Specifically, ananti-angiogenesis activity was shown for both a PGA-PTX−E-[c(RGDfk)₂]conjugate (SEQ ID NO:18) having a 3.9 mol % E-[c(RGDfk)₂] and 5.5 mol %PTX loading (see, FIGS. 12 and 14-16) as well as for thePGA-PTX−E-[c(RGDfk)₂] conjugate (SEQ ID NO:18) having a 5 mol %E-[c(RGDfk)₂] and 2.6 mol % PTX loading (see, FIGS. 13A and 15).

As further demonstrated in the Examples section that follows, theArg-Gly-Asp (RGD)-containing moiety (SEQ ID NO: 1), for exampleE-[(cRGDfk)₂] (SEQ ID NO: 2), has inherent anti-angiogenesischaracteristic namely the inhibition of endothelial cell migrationtoward the chemoattractant VEGF and attachment to fibrinogen coatedplates (see, FIGS. 14 and 15). No antagonistic activity of theArg-Gly-Asp (RGD)-containing moiety (SEQ ID NO:1) against theanti-angiogenesis activity of Paclitaxel was observed, as assessed bythe anti-proliferative activity against HUVEC, but rather theanti-proliferative activity of the E-[(cRGDfk)₂] (SEQ ID NO:2) andPaclitaxel, when the cells were subjected to both drugs together, wasadditive in nature (see, FIG. 12).

Cyr61 (also known as CCN1) is a Cysteine-rich matricellular protein thatsupports cell adhesion and induces adhesion signaling. Furthermore,Cyr61 stimulates endothelial cell migration and enhances growth factorinduced DNA synthesis in culture and therefore induces angiogenesis invivo. Mechanistically, Cyr61 acts as a non-RGD-containing ligand ofintegrin receptors. Functional blockade of αvβ₃, a Cyr61 integrinreceptor, is specifically cytotoxic towards Cyr61-overexpressing breastcancer cells and a specific αvβ₃-RGD peptidomimetic agent (SEQ ID NO:28) prevents αvβ3 from binding to its ligand, Cyr61. It has beenrecently shown that Cyr61 overexpression can render human breast cancercells highly resistant to Paclitaxel.

In some embodiments, the conjugates described herein act as specificantagonists of αvβ3 and consequently inhibit the Cyr61-integrin receptorsignal transduction cascade, thereby serving to inhibit Cyr-61 dependentcancer cell growth and chemoresistance.

In some embodiments, the polymeric conjugates described herein arecomposed of a polymeric backbone, formed from a plurality of backboneunits that are covalently linked to one another, wherein at least aportion of this plurality of backbone units has a therapeutically activeagent, as described herein, attached thereto, and at least anotherportion of the plurality of backbone units has the angiogenesistargeting moiety (the RGD containing moiety, (SEQ ID NO:1) as describedherein), attached thereto.

Those backbone units that have the therapeutically active agent attachedthereto and those backbone units that have the angiogenesis targetingmoiety attached thereto can be randomly dispersed within the polymericbackbone.

The polymeric backbone can further include non-functionalized backboneunits, as discussed hereinbelow, to which none of the therapeuticallyactive agent and the angiogenesis targeting moiety are attached.

In some embodiments, the polymeric backbone of the conjugates describedconstitutes polymers (or co-polymers) to which the angiogenesistargeting moiety and the therapeutically active agent are attached.

Polymers which are suitable for use in the context of the presentembodiments are biocompatible, non-immunogenic and non-toxic. Thepolymers serve as carriers that enable specific delivery into tumortissue. As described hereinabove, the specific delivery is due to theenhanced permeability and retention (EPR) effect discussed hereinabove.Furthermore, conjugation to polymers should restrict the passage throughthe blood brain barrier and would prolong the circulating half-life ofthe drugs, hence inhibiting the growth of tumor endothelial andepithelial cells by exposing the cells to the conjugated drugs in thecirculation for a longer time compared to the free drugs. Additionally,polymer-drug conjugates may act as drug depots for sustained release,producing prolonged drug exposure to tumor cells. Finally, water solublepolymers (e.g., water soluble polyamino acids) may be used to stabilizedrugs, as well as to solubilize otherwise insoluble compounds such as,for example TNP-470 and Paclitaxel.

As used herein, the term “polymer” describes an organic substancecomposed of a plurality of repeating structural units (backbone units)covalently connected to one another. The term “polymer” as used hereinencompasses organic and inorganic polymers and further encompasses oneor more of a homopolymer, a copolymer or a mixture thereof (a blend).The term “homopolymer” as used herein describes a polymer that is madeup of one type of monomeric units and hence is composed of homogenicbackbone units. The term “copolymer” as used herein describes a polymerthat is made up of more than one type of monomeric units and hence iscomposed of heterogenic backbone units. The heterogenic backbone unitcan differ from one another by the pendant groups thereof.

The polymer is comprised of backbone units formed by polymerizing thecorresponding monomeric units whereby the therapeutically active agentand the angiogenesis targeting moiety are attached to at least a portionof these backbone units. Some or all of these backbone units aretypically functionalized prior to conjugation so as to have a reactivegroup for attaching the anti-angiogenesis agent and the bone targetingmoiety. Those backbone units that are not functionalized and/or do notparticipate in the conjugations of the therapeutically active agent andthe angiogenesis targeting moiety are referred to herein as “free”backbone units.

The polymer may be a biostable polymer, a biodegradable polymer or acombination thereof. The term “Biostable” describes a compound that isnot degraded in vivo, i.e., is not biodegradable.

The term “biodegradable”, describes a substance that which can decomposeunder physiological and/or environmental conditions into breakdownproducts. Such physiological and/or environmental conditions include,for example, hydrolysis (decomposition via hydrolytic cleavage),enzymatic catalysis (enzymatic degradation), and mechanicalinteractions. This term typically refers to substances that decomposeunder these conditions such that 50 weight percents of the substancedecompose within a time period shorter than one year.

The polymers can be water-soluble or water-insoluble. In someembodiments, the polymers are water soluble at room temperature.

The polymers can further be charged polymers or non-charged polymers.Charged polymers can be cationic polymers, having positively chargedgroups and a positive net charge at a physiological pH; or anionicpolymers, having negatively charged groups and a negative net charge ata physiological pH. Non-charged polymers can have positively charged andnegatively charged group with a neutral net charge at physiological pH,or can be non-charged.

In some embodiments, the polymer has an average molecular weight in therange of 100 Da to 800 kDa. In some embodiments, the polymer has anaverage molecular weight lower than 100 kDa or lower than 60 kDa. Insome embodiments, the polymer's average molecular weight range is 10 kDato 40 kDa.

Polymeric substances that have a molecular weight higher than 10 kDatypically exhibit an EPR effect, as described herein, while polymericsubstances that have a molecular weight of 100 kDa and higher haverelatively long half-lives in plasma and an inefficient renal clearance.Accordingly, a molecular weight of a polymeric conjugate can bedetermined while considering the half-life in plasma, the renalclearance, and the accumulation in the tumor of the conjugate.

The polymer used in the context of embodiments of the invention can be asynthetic polymer or a naturally-occurring polymer. In some embodiments,the polymer is a synthetic polymer.

The polymeric backbone of the polymer described herein may be derivedfrom, for example, polyacrylates, polyvinyls, polyamides, polyurethanes,polyimines, polysaccharides, polypeptides, polycarboxylates, andmixtures thereof.

Exemplary polymers which are suitable for use in the context of thepresent embodiments include, but are not limited to, dextran, a watersoluble polyamino acid, a polyethylenglycol (PEG), a polyglutamic acid(PGA), a polylactic acid (PLA) a polylactic-co-glycolic acid (PLGA), apoly(D,L-lactide-co-glycolide) (PLA/PLGA), apoly(hydroxyalkylmethacrylamide), a polyglycerol, a polyamidoamine(PAMAM), and a polyethylenimine (PEI).

In some embodiments, the polymeric backbone is derived from apoly(hydroxyalkylmethacrylamide) or a copolymer thereof. Such apolymeric backbone comprises methacrylamide backbone units.

Poly(hydroxyalkylmethacrylamide) (HPMA) polymers are a class ofwater-soluble synthetic polymeric carriers that have been extensivelycharacterized as biocompatible, non-immunogenic and non-toxic. Oneadvantage of HPMA polymers over other water-soluble polymers is thatthey may be tailored through relatively simple chemical modifications,in order to regulate their respective drug and targeting moiety content.Further, the molecular weight and charge of these polymers may bemanipulated so as to allow renal clearance and excretion from the body,or to alter biodistribution while allowing tumor targeting.

According to some embodiments, the polymer is Polyglutamic acid (PGA).

The chemical structure of PGA is shown in FIG. 2A. PGA contains a largenumber of side chain carboxylic functional groups which can be readilyutilized for drug attachment. PGA can be readily degraded by lysosomalenzymes such as Cathepsin B, to its nontoxic basic components,L-glutamic acid, D-glutamic acid and D,L-glutamic acid. Sodium glutamatehas been reported to prevent manifestations of neuropathy induced byPaclitaxel, thus enabling higher doses of Paclitaxel to be tolerated.

As used herein, “a polyglutamic acid” or “polyglutamic acid polymer”encompasses poly(L-glutamic acid), poly(D-glutamic acid),poly(D,L-glutamic acid), poly(L-gamma glutamic acid), poly(D-gammaglutamic acid) and poly(D,L-gamma glutamic acid).

In some embodiments, the polyglutamic acid comprises at least 50% of itsbackbone units as glutamic acid, and optionally comprises, 60, 70, 80,90 or 100% of its backbone units as glutamic acid. The polyglutamic acidcan be substituted by naturally occurring or chemically modified aminoacids, preferably hydrophilic amino acids, provided that when conjugatedto the therapeutically active agent and the angiogenesis targetingmoiety, the substituted polyglutamic acid polymeric backbone hasimproved aqueous solubility and/or improved efficacy relative to theunconjugated therapeutic agent, and is preferably non-immunogenic. Up to50% of the backbone units of the polyglutamic acid polymeric backbonecan be substituted.

A representative general formula of a polyglutamic acid based conjugatewherein the polymeric backbone has a therapeutically active agentconjugated thereto through a degradable linker and further has anangiogenesis targeting moiety conjugated thereto, is shown in FIG. 1.

According to some embodiments, the polymer is polyethylenglycol (PEG).

PEG is a unique polyether diol, usually manufactured by the aqueousanionic polymerization of ethylene oxide, although other polymerizationinitiators can be employed. This polymer is amphiphilic and dissolves inorganic solvents as well as in water; it is also non-toxic and iseliminated by a combination of renal and hepatic pathways. Furthermore,PEG has the lowest level of protein or cellular absorption of any knownpolymer and hence is advantageous for drug conjugation. The structure ofa PEG based conjugate, according to the embodiments of the presentinvention, is shown in FIG. 5.

It is to be understood that the polymers as discussed herein describethose polymers that are formed from homogenic or heterogenic,non-functionalized monomeric units, and that the polymeric backboneconstituting the polymeric conjugate corresponds to such polymers bybeing comprised of the same monomeric units, while some of thesemonomeric units are functionalized, as described herein. Thus, thepolymeric backbone of the polymeric conjugate is similar to that of thepolymers described herein, and differs from the polymers by having theabove-described agents attached to some of the backbone units therein.

As discussed hereinabove, the tumor vasculature possesses an enhancedcapacity for the uptake of macromolecules and colloidal drug carriershaving a high molecular weight and large hydrodynamic diameter due tothe EPR effect. Therefore, a conjugate as described herein, having alarge enough hydrodynamic diameter is beneficial. The term “largeenough” is used herein to describe a conjugate having a hydrodynamicdiameter which leads to an increase in the ratio of conjugateaccumulated in the tumor tissue as compared to other tissues. Thedetermination of the optimal ratio is well within the capability ofthose skilled in the art. For example, the ratio may be 1.1, 2, 3, 4, 5etc. In some embodiments, the hydrodynamic diameter is in the range offrom 10 nm to 200 nm. In some embodiments, the hydrodynamic diameter isin the range of from 10 nm to 100 nm. In some embodiments thehydrodynamic diameter is in the range of from 20 nm to 50 nm. In yetanother embodiment the hydrodynamic diameter is 40 nm. In yet anotherembodiment the hydrodynamic diameter is 30 nm. The hydrodynamic diametercan be measured as described below under the Materials and Methods ofthe Example section which follows hereinbelow. The hydrodynamic diameterof nano-scale particles of a Polyglutamate copolymer to which Paclitaxeland a bis-cyclic RGD containing peptide (PGA-PTX−E-[c(RGDfk)_(2]); SEQID NO:18) were conjugated to the polymeric backbone as well as aPolyglutamate copolymer to which Paclitaxel and a monocyclic RGDcontaining peptide (PGA-PTX−c[RGDfk]; SEQ ID NO:16) was conjugated tothe polymeric backbone is shown in FIG. 9.

In each of the conjugates described herein, the therapeutically activeagent and the angiogenesis targeting moiety can each be linked to therespective portion of the backbone units in the polymeric backbonedirectly, or indirectly, through a linker moiety (also referred toherein as a linker, a linker group or a linking group), whereby, in someembodiments, the direct/indirect linkage is designed as being cleavableat conditions characterizing the desired bodily site (e.g., by certainenzymes or pH), as detailed hereinbelow.

Hence, according to some embodiments, at least one of thetherapeutically active agent and the targeting moiety is attached to thepolymer via a linker. In some embodiments, each of the therapeuticallyactive agent and the targeting moiety is attached to the polymer via alinker. The linker linking the therapeutically active agent to thepolymer and the linker linking the angiogenesis targeting moiety to thepolymer may be the same or different.

The linker described herein refers to a chemical moiety that serves tocouple the angiogenesis targeting moiety and/or the therapeuticallyactive agent to the polymeric backbone while not adversely affectingeither the targeting function of the angiogenesis targeting moiety orthe therapeutic effect of the angiogenesis targeting moiety and/ortherapeutically active agent.

In some embodiments, the linker is a biodegradable linker.

The phrase “biodegradable linker”, as used herein, describes a linkerthat is capable of being degraded, or cleaved, when exposed tophysiological conditions. Such physiological conditions can be, forexample, pH, a certain enzyme, and the like.

In some embodiments, the linker is capable of being cleaved bypre-selected cellular enzymes, for instance, those found in osteoblasts,osteoclasts, lysosomes of cancerous cells or proliferating endothelialcells. Alternatively, an acid hydrolysable linker could comprise anester or amide linkage and be for instance, a cis-aconityl linkage. Suchlinkers further enhance the therapeutic activity and reduced toxicity ofthe conjugates described herein, by allowing the release of theanti-angiogenesis drug and/or the alendronate only at the desired bodilysite.

Accordingly, according to some embodiments, the biodegradable linker isa pH-sensitive linker or an enzymatically-cleavable linker.

A pH-sensitive linker comprises a chemical moiety that is cleaved ordegraded only when subjected to a certain pH condition, such as acidicpH (e.g., lower than 7), neutral pH (6.5-7) or basic pH (higher than 7).

Such a linker may, for example, be designed to undergo hydrolysis underacidic or basic conditions, and thus, the conjugate remains intact anddoes not release the agents attached to the polymer in the body, untilits reaches a physiological environment where a pH is either acidic orbasic, respectively.

Exemplary pH-sensitive linkers include, but are not limited to ahydrazone bond, an ester (including orthoester) bond, an amide bond of,for example, a cis-aconytil residue, a trityl group, an acetal, a ketal,an Alanine ester, a Gly-ester and a -[Gly-Phe-Gly]-moiety (SEQ ID NO:29).

In some embodiments the biodegradable linker is anenzymatically-cleavable linker. Such a linker is typically designed soas to include a chemical moiety, typically, but not exclusively, anamino acid sequence that is recognized by a pre-selected enzyme. Such anamino acid sequence is often referred to in the art as a “recognitionmotif”. A conjugate comprising such a linker typically remainssubstantially intact in the absence of the pre-selected enzyme in itsenvironment, and hence does not cleave or degrade so as to the releasethe agent attached thereto until contacted with the enzyme.

In some embodiments, the enzymatically cleavable linker is cleaved by anenzyme which is overexpressed in tumor tissues. A conjugate comprisingsuch a linker ensures, for example, that a substantial amount of theconjugated therapeutically active agent is released from the conjugateonly at the tumor tissue, thus reducing the side effects associated withnon-selective administration of the drug and further enhancing theconcentration of the drug at the tumor site.

Exemplary enzymes which are suitable for use in the context of theseembodiments include, but are not limited to the group consisting ofCathepsin B, Cathepsin K, Cathepsin D, Cathepsin H, Cathepsin L,legumain, MMP-2 and MMP-9.

Suitable linkers include, but are not limited to, alkyl chains; alkylchains optionally substituted with one or more substituents and in whichone or more carbon atoms are optionally interrupted by a nitrogen,oxygen and/or sulfur heteroatom.

Other suitable linkers include amino acids and/or oligopeptides.

Such alkyl chains and/or oligopeptides can optionally be functionalizedso as allow their covalent binding to the moieties linked thereby (e.g.,the polymeric backbone and the targeting moiety, the polymer and thetherapeutically active agent). Such a functionalization may includeincorporation or generation of reactive groups that participate in suchcovalent bindings, as detailed hereinunder.

In some embodiment, the linker is a biodegradable oligopeptide whichcontains, for example, from 2 to 10 amino acid residues.

In some embodiments, the linker is a Cathepsin B-cleavable linker.

Cathepsin B is a lysosomal enzyme overexpressed in both epithelial andendothelial tumor cells. Suitable linkers having cathepsin-B cleavablesites include amino acid sequences such as, but are not limited to-[Cit-Val]-(SEQ ID NO: 29), -[Arg]-, -[Arg-Arg]-(SEQ ID NO:31),-[Phe-Lys]-(SEQ ID NO:12), [Gly-Phe-Leu-Gly] (SEQ ID NO: 10),-[Gly-Phe-Ala-Leu]-(SEQ ID NO: 32) and -[Ala-Leu-Ala-Leu]-(SEQ ID NO:33), -[Gly-Leu-Gly]-(SEQ ID NO: 34), -[Gly-Phe-Gly]-(SEQ ID NO: 35),-[Gly-Phe-Leu-Gly-Phe-Lys]-(SEQ ID NO: 36) and combinations thereof.

In some embodiments the linker comprises the amino acid sequences-[Gly-Leu-Gly]-(SEQ ID NO: 34), -[Gly-Phe-Gly]-(SEQ ID NO: 35),-[Gly-Leu-Phe-Gly]-(SEQ ID NO: 37), -[Gly-Phe-Leu-Gly]-(SEQ ID NO: 10),-[Phe-Lys]-(SEQ ID NO: 12) and -[Gly-Phe-Leu-Gly-Phe-Lys]-(SEQ ID NO:36). In some embodiments, the linker consists of these amino acidsequences or a combination thereof.

As discussed hereinabove, PGA can be readily degraded by Cathepsin B, toits nontoxic basic components, L-glutamic acid, D-glutamic acid andD,L-glutamic acid.

As demonstrated in the Examples section that follows, Cathepsin Breleases the anti-angiogenesis agent Paclitaxel from a conjugate of thedrug with PGA polymer (see, FIG. 10).

Matrix metalloproteinases (MMP), in particular MMP-2 and MMP-9, havebeen identified as important proteases for the progression of malignanttumors. Suitable linkers having MMP-2 and MMP-9 cleavable sites include,but are not limited to, -[Gly-Pro-Gln-Gly-Ile-Ala-Gly-Gln]-(SEQ IDNO:38), -[Gly-Pro-Leu-Gly-Ile-Ala-Gly-Gln]-(SEQ ID NO:11), (SEQ IDNO:39) and combinations thereof.

In some embodiments, the linker comprises -[Gly-Phe-Leu-Gly]-(SEQ IDNO:10).

In some embodiments the linker comprises-[Gly-Pro-Leu-Gly-Ile-Ala-Gly-Gln]-(SEQ ID NO:11).

An oligopeptide linker which contains the pre-selected amino acidsequence (recognition motif) can also be constructed such that therecognition motif is repeated several times within the linker, tothereby enhance the selective release of the attached agent. Variousrecognition motifs of the same or different enzymes can also beincorporated within the linker. Similarly, the linker may comprisemultiple pH sensitive bonds or moieties. Linkers comprising suchmultiple cleavable sites can enhance the selective release of thetherapeutically active agent at the desired bodily site, therebyreducing adverse side effects, and further enhance the relativeconcentration of the released drug at the bodily site when it exhibitsits activity.

In cases where the angiogenesis targeting moiety and/or thetherapeutically active agent is bound directly to the polymericbackbone, the bond linking these moieties can also be biodegradable, forexample, an enzymatically-cleavable bond or a pH-sensitive bond. Such abond can be formed upon functionalizing the polymeric backbone, theangiogenesis targeting moiety and/or the therapeutically active agent,so as to include compatible reactive groups, as defined herein, forforming the required bond.

The peptide linker may also include a peptide sequence which serves toincrease the length of the linker. Longer peptides may be advantageousdue to a more efficient steric interaction of the linker with thecleaving enzyme due to enhanced accessibility.

In some embodiments the angiogenesis targeting moiety is linked to thepolymeric backbone or to the linker via a spacer. In some embodimentsthe therapeutically active agent is linked to the polymeric backbone orto the linker via a spacer. The spacers can be the same or different.

The term “spacer” as used herein describes a chemical moiety that iscovalently attached to, and interposed between, the polymeric backboneand the linker, or the angiogenesis targeting moiety/therapeuticallyactive agent thereby forming a bridge-like structure between thepolymeric backbone and/or the angiogenesis targetingmoiety/therapeutically active agent. Alternatively, the spacer may becovalently attached to, and interposed between, the linker and thetherapeutically active agent and/or the angiogenesis targeting moiety.

Hence, according to some embodiments at least one of the therapeuticallyactive agent and the angiogenesis targeting moiety is attached to thepolymeric backbone and/or to the linker via a spacer.

Suitable spacers include, but are not limited to, alkylene chains,optionally substituted by one or more substituents and which areoptionally interrupted by one or more nitrogen, oxygen and/or sulfurheteroatom.

Other suitable spacers include amino acids and amino acid sequences,optionally functionalized with one or more reactive groups for beingcoupled to the polymeric backbone/angiogenesis targetingmoiety/therapeutically active agent/linkers.

In some embodiments, the spacer has the formula G-(CH₂)n-K, wherein n isan integer from 1 to 10; and G and K are each a reactive group such as,for example, NH, O or S. In some embodiments, G and K are each NH and nis 2.

An exemplary spacer is —[NH—(CH₂)_(m)NH₂]— wherein “m” stands for aninteger ranging from 1-10. Preferably m is 2. A conjugate wherein thespacer linking the anti-angiogenesis agent (i.e. TNP470) to aPolyglutamate polymeric unit is -[NH—(CH₂)₂NH₂]— is shown in FIGS. 4B,4C and 4D.

In some embodiments, the spacer is an amino acid sequence, optionally aninert amino acid sequence (namely, does not affect the affinity orselectivity of the conjugate). Such a spacer can be utilized forelongating or functionalizing the linker.

In some embodiments, the spacer is a glutamate residue (-E-). Forexample, a conjugate wherein the spacer linking the angiogenesistargeting moiety to a polyglutamate polymeric backbone is a glutamateresidue (-E-), is shown in FIG. 4D.

In some cases, a spacer is utilized for enabling a more efficient andsimpler attachment of the angiogenesis targeting moiety and/ortherapeutically active agent to the polymeric backbone or linker, interms of steric considerations (renders the site of the polymer to whichcoupling is effected less hindered) or chemical reactivityconsiderations (adds a compatible reactive group to the site of thepolymer to which coupling is effected). In some cases, the spacer maycontribute to the performance of the resulting conjugate. For example,the spacer may render an enzymatically cleavable spacer less stericallyhindered and hence more susceptible to enzymatic interactions.

In some cases the spacer is utilized for enabling a more efficient andsimpler synthesis of the conjugate by altering the solubility of thetherapeutically active agent and/or the angiogenesis targeting moietiesto which the spacer is attached (i.e. either more hydrophobic or morehydrophilic).

In some embodiments, the spacer is a degradable spacer, which is capableof undergoing degradation reactions so as to release the agent attachedthereto. In some embodiments, the spacer is biodegradable, as definedherein.

In some embodiments, the spacer is a multivalent moiety that is used soas to attach two or more moieties to a backbone unit in the polymericbackbone. Exemplary such a spacer is a glutamate residue, which is used,for example, to attach two cyclic RGD-containing moieties to a polymericbackbone.

A spacer may also be used in order to attach other agents (e.g., alabeling agent, as described hereinbelow) to the conjugate.

The spacer may be varied in length and in composition, depending onsteric consideration and may be used to space the angiogenesis targetingmoiety and/or therapeutically active agent form the polymeric backbone.

As discussed hereinabove, the optimal degree of loading of thetherapeutically active agent and the angiogenesis targeting moiety isdetermined empirically based on the desired properties of the conjugate(e.g., water solubility, therapeutic efficacy, pharmacokineticproperties, toxicity and dosage requirements), and syntheticconsiderations (e.g., the amount of the conjugated moiety that can beconjugated to the polymeric backbone in the synthesis mode utilized).

The number of backbone units within the polymeric backbone that have atherapeutically active agent conjugated thereto is defined herein as“y”, the number of backbone units within the polymeric backbone thathave an angiogenesis targeting moiety conjugated thereto is hereindefined as “w” and the number of free backbone units in the polymericbackbone (which are not bound to an additional moiety) is herein definedas “x”.

According to some embodiments, the conjugate described herein can berepresented by the general formula I:

[A₁]x[A₂-L₁-B]y[A₃-L₂-D]w  Formula I

wherein:

x is an integer having a value such that x/(x+y+w) multiplied by 100 isin the range of from 0.01 to 99.9;

y is an integer having a value such that y/(x+y+w) multiplied by 100 isin the range of from 0.01 to 99.9;

w is an integer having a value such that w/(x+y+w) multiplied by 100 isin the range of from 0.01 to 99.9;

A₁, A₂ and A₃ are each backbone units covalently linked to one anotherand forming the polymeric backbone, wherein:

B is the therapeutically active agent, as described herein;

D is the angiogenesis targeting moiety, as described herein; each of theL₁ and L₂ is independently the linker as described herein or is absent;

such that [A₂-L₁-B] is a backbone unit having attached thereto theanti-angiogenesis agent; and

[A₃-L₂-D] is a backbone unit having attached thereto the bone targetingmoiety;

wherein each of the [A₁], the [A₂-L₁-D] and the [A₃-L₂-D] is either aterminal backbone unit being linked to one of the [A₁], the [A₂-L₁-D]and the [A₃-L₂-D], or is linked to at least two of the [A₁], the[A₂-L₁-D] and the [A₃-L₂-D] and the A₁, A₂ and/or A₃ are linked to oneanother to thereby form the polymeric backbone.

In some embodiments where the polymeric conjugate is derived from HPMA,A₁ is a hydroxypropylmethacrylamide unit; and A₂ and A₃ are amethacrylamide unit.

In some embodiments where the polymeric conjugate is derived from PGA,A₁ is a glutamate unit.

According to some embodiments, the conjugate described herein can berepresented by the general formula II:

wherein B, D, L¹, L² and w, x, y, are as defined herein.

According to some embodiments, the conjugate described herein can berepresented by the general formula III:

wherein B, D, L¹, L² and w, x, y, are as defined herein.

In some embodiments, the conjugate has the structure:

wherein w, x and y are as defined herein.

In some embodiments, the conjugate has the structure:

wherein w, x and y are as defined herein.

According to some embodiments of the present invention, x is an integerhaving a value such that x/(x+y+w) multiplied by 100 is in the range offrom 70 to 99.9; y is an integer having a value such that y/(x+y+w)multiplied by 100 is in the range of from 0.01 to 15; and w is aninteger having a value such that w/(x+y+w) multiplied by 100 is in therange of from 0.01 to 15.

For example x/(x+y+w) multiplied by 100 may be 71, 72, 73, 74, 75, 76,77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94,95, 96, 97, 98, 99 or 99.9; y/(x+y+w) multiplied by 100 may be 0.01,0.02, 0.03, 0.04, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1,2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15; and w/(x+y+w)multiplied by 100 may be 0.01, 0.02, 0.03, 0.04, 0.05, 0.1, 0.2, 0.3,0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,14 or 15.

According to some embodiments, the conjugate described herein furthercomprises a labeling agent attached thereto.

In some embodiments, the labeling agent is attached to a portion of thebackbone units that do not have the therapeutically active agent or thetargeting moiety attached thereto. Optionally, the labeling agent isattached to any one of a linker, a spacer or the therapeutically activeagent or the targeting moiety. The attachment of a labeling agent to theconjugate enables utilizing these conjugates for monitoring medicalconditions associated with angiogenesis, for example, monitoring thetherapeutic effect exhibited by the conjugate described herein.

As used herein, the phrase “labeling agent” describes a detectablemoiety or a probe. Exemplary labeling agents which are suitable for usein the context of the these embodiments include, but are not limited to,a fluorescent agent, a radioactive agent, a magnetic agent, achromophore, a bioluminescent agent, a chemiluminescent agent, aphosphorescent agent and a heavy metal cluster.

The phrase “radioactive agent” describes a substance (i.e. radionuclideor radioisotope) which loses energy (decays) by emitting ionizingparticles and radiation. When the substance decays, its presence can bedetermined by detecting the radiation emitted by it. For these purposes,a particularly useful type of radioactive decay is positron emission.Exemplary radioactive agents include ^(99m)Tc, ¹⁸F, ¹³¹I and ¹²⁵I.,

The term “magnetic agent” describes a substance which is attracted to anexternally applied magnetic field. These substances are commonly used ascontrast media in order to improve the visibility of internal bodystructures in Magnetic Resonance Imaging (MRI). The most commonly usedcompounds for contrast enhancement are gadolinium-based. MRI contrastagents alter the relaxation times of tissues and body cavities wherethey are present, which, depending on the image weighting, can give ahigher or lower signal.

As used herein, the term “chromophore” describes a chemical moiety that,when attached to another molecule, renders the latter colored and thusvisible when various spectrophotometric measurements are applied.

The term “bioluminescent agent” describes a substance which emits lightby a biochemical process

The term “chemiluminescent agent” describes a substance which emitslight as the result of a chemical reaction.

The phrase “fluorescent agent” refers to a compound that emits light ata specific wavelength during exposure to radiation from an externalsource.

The phrase “phosphorescent agent” refers to a compound emitting lightwithout appreciable heat or external excitation as by slow oxidation ofphosphorous.

A heavy metal cluster can be for example a cluster of gold atoms used,for example, for labeling in electron microscopy techniques.

Each of the conjugates described herein may further include anadditional moiety conjugated thereto. Such an additional moiety can beconjugated either to backbone units within and throughout the polymericbackbone, or be attached at one or both ends of the polymeric backbone.

Such an additional moiety can be a labeling agent, as described herein,or an additional targeting moiety or an additional therapeuticallyactive agent, which may improve the performance of the formed conjugate.Such an additional moiety can further be a moiety that improves thesolubility, bioavailability, and/or any other desired feature of theformed conjugate.

As discussed hereinabove, the conjugates described herein comprise apolymer having tumor targeting characteristics (due to the EPR effect),an angiogenesis targeting moiety and an anti-canceragent/anti-angiogenesis agent. Therefore, the conjugates describedherein are targeted to bodily sites characterized by angiogenesis and orcancer tissue. As further described hereinabove, the conjugatesdescribed herein are capable of inhibiting angiogenesis as well as cellproliferation and therefore can be utilized for the treatment of diseaseconditions characterized by pathologically excessive angiogenesiswherein the inhibition of angiogenesis and/or cell proliferation isbeneficial.

Pathological angiogenesis has been demonstrated in several diseases,such as cancer, hypertension, rheumatoid arthritis, and diabeticretinopathy. Tumor growth and metastasis are particularly dependent onthe degree of angiogenesis. Tumor angiogenesis is the proliferation of anetwork of blood vessels that penetrate into cancerous tumors in orderto supply nutrients and oxygen and remove waste products, thus leadingto tumor growth. Tumor angiogenesis involves hormonal stimulation andactivation of oncogenes, expression of angiogenic growth factors,extravasation of plasma protein, deposition of a provisionalextracellular matrix (ECM), degradation of ECM, and migration,proliferation and elongation of endothelial capillaries. Inhibition offurther vascular expansion has therefore been the focus of activeresearch for cancer therapy.

As demonstrated in the Examples section that follows, the conjugatesdescribed herein were able to exhibit anti-angiogenesis activity.

Thus, according to another aspect of embodiments of the invention thereis provided a method of treating a medical condition associated withangiogenesis in a subject in need thereof. The method is effected byadministering to the subject a therapeutically effective amount of anyof the conjugates described herein.

Accordingly, according to another aspect of some embodiments of thepresent invention there are provided uses of the conjugates describedherein as a medicament. In some embodiments, the medicament is fortreating a medical condition associated with angiogenesis.

According to another aspect of some embodiments of the presentinvention, the conjugates described herein are identified for use in thetreatment of a medical condition associated with angiogenesis.

As used herein, the term “method” refers to manners, means, techniquesand procedures for accomplishing a given task including, but not limitedto, those manners, 30 means, techniques and procedures either known to,or readily developed from known manners, means, techniques andprocedures by practitioners of the chemical, pharmacological,biological, biochemical and medical arts.

As used herein, the term “treating” includes abrogating, substantiallyinhibiting, slowing or reversing the progression of a condition,substantially ameliorating clinical or aesthetical symptoms of acondition or substantially preventing the appearance of clinical oraesthetical symptoms of a condition.

It is understood that the conjugates of the present invention may beadministered in conjunction with other drugs, including otheranti-cancer and anti-angiogenesis drugs. Such combinations are known inthe art.

When the treatable condition is cancer the term would encompass anyinhibition of tumor growth or metastasis, or any attempt to inhibit,slow or abrogate tumor growth or metastasis. The method includes killingcancer cells by non-apoptotic as well as apoptotic mechanisms of celldeath.

It is noted herein that by targeting a therapeutically active agent viathe methodologies described herein, the toxicity of the therapeuticallyactive agent is substantially reduced, due to the conjugate selectivitytowards sites of excessive angiogenesis. Consequently, besides the useof the conjugates described herein in a clinically evident disease,optionally in combination with other drugs, these conjugates maypotentially be used as a long term-prophylactic for individuals who areat risk for relapse due to residual dormant cancers. The use ofnon-toxic targeted conjugates for the treatment of asymptomaticindividuals who are at risk for relapse of a cancer, may lead to a majorparadigm shift in cancer treatment from current methods where treatmentis generally not initiated until the cancer becomes clinically evident.

The term “cancer cells” describes a group of cells which displayuncontrolled growth (division beyond the normal limits).

The phrase “therapeutically effective amount” describes the amount of acompound which is sufficient to effect treatment when administered to asubject in need of such treatment or prevention. As used herein thisphrase describes the amount of conjugate which is sufficient to reduceor prevent angiogenesis (i.e. inhibit the formation of new blood vesselsin a tissue) and/or cell proliferation and/or kill preexisting cancercells in tissue.

Medical conditions associated with angiogenesis and which are treatableby the conjugates described herein include, but are not limited to,atherosclerosis, cancer, hypertension, rheumatoid arthritis, diabetesand diabetes related complications such as diabetic retinopathy andmacular degeneration (MD). The terms “cancer” and “tumor” are usedinterchangeably herein to describe a class of diseases in which a groupof cells display uncontrolled growth (division beyond the normallimits). The term “cancer” encompasses malignant and benign tumors aswell as disease conditions evolving from primary or secondary tumors.The term “malignant tumor” describes a tumor which is not self-limitedin its growth, is capable of invading into adjacent tissues, and may becapable of spreading to distant tissues (metastasizing). The term“benign tumor” describes a tumor which is not malignant (i.e. does notgrow in an unlimited, aggressive manner, does not invade surroundingtissues, and does not metastasize). The term “primary tumor” describes atumor that is at the original site where it first arose. The term“secondary tumor” describes a tumor that has spread from its original(primary) site of growth to another site, close to or distant from theprimary site.

Cancers treatable by the conjugates described herein include, but arenot limited to, solid, including carcinomas, and non-solid, includinghematologic malignancies. Carcinomas include and are not limitedadenocarcinomas and epithelial carcinomas. Hematologic malignanciesinclude leukemias, lymphomas, and multiple myelomas. The following arenon-limiting examples of the cancers treatable with the conjugatesdescribed herein: ovarian, pancreas, brain, colon, rectal, colorectal,melanoma, lung, breast, kidney, and prostate cancers.

The term “cancer metastases” describes cancer cells which have “brokenaway”, “leaked”, or “spilled” from a primary tumor, entered thelymphatic and/or blood vessels, circulated through the lymphatic systemand/or bloodstream, settled down and proliferated within normal tissueselsewhere in the body thereby creating a secondary tumor.

The term “arteriosclerosis” describes a hardening of the arteries, andoccurs when the normal lining of the arteries deteriorates, the walls ofarteries thicken, and deposits of fat and plaque build up, causingnarrowing (or even blockage) of the arteries. Atherosclerosis is theleading cause of heart attacks, heart disease and strokes. Essentially,the plaque build-up on the arterial walls becomes so significant that itbegins to block the flow of blood. When vital organs, such as the heartor lungs, are deprived of oxygen rich blood, atherosclerosis becomes alife-threatening condition. Other complications of atherosclerosis aredetachment of plaque build up and blood clots that travel and becomelodged elsewhere in the body.

The term “diabetes” is used interchangeably with the term “diabetesmellitus” and describes a metabolic disorder of multiple etiologycharacterized by chronic hyperglycaemia with disturbances ofcarbohydrate, fat and protein metabolism resulting from defects ininsulin secretion, insulin action, or both. The effects of diabetesmellitus include long-term damage, dysfunction and failure of variousorgans. Presently, diabetes mellitus is classified into type I and typeII. The majority of patients with type I diabetes have autoimmunedestruction of pancreatic beta cells as the underlying cause, have anabsolute requirement for insulin therapy and will develop ketoacidosiswithout treatment. In type II, there is relative insulin deficiency andresistance to insulin. A causal association between glycemic control andthe development and progression of the microvascular complications i.e.(retinopathy, nephropathy and neuropathy) is well-established. By virtueof microvascular involvement any tissue can be effected by diabetes.

The term “diabetes” encompasses diabetes related complications which aremainly caused by damage to blood vessels (angiopathy). Exemplarydiabetes complications include, but are not limited to diabeticretinopathy (damage to the retina), which can eventually lead toblindness; diabetic neuropathy which is characterized by abnormal anddecreased sensation, usually in a ‘glove and stocking’ distributionstarting with the feet but potentially in other nerves, later oftenfingers and hands; diabetic nephropathy characterized by damage to thekidney which can lead to chronic renal failure; and diabetic cardiopathywhich is characterized by damage to the heart leading to diastolicdysfunction and eventually heart failure.

The term “hypertension” describes a medical condition in which the bloodpressure is chronically elevated. In current usage, the word“hypertension” without a qualifier normally refers to systemic, arterialhypertension. Hypertension can be classified as either essential(primary) or secondary. Essential hypertension indicates that nospecific medical cause can be found to explain a patient's condition. About 95% of hypertension is essential hypertension. Secondaryhypertension indicates that the high blood pressure is a result of(i.e., secondary to) another condition, such as kidney disease or tumors(adrenal adenoma or pheochromocytoma). Persistent hypertension is one ofthe risk factors for strokes, heart attacks, heart failure and arterialaneurysm, and is a leading cause of chronic renal failure.

The term “rheumatoid arthritis” describes is a chronic, systemicinflammatory disorder that may affect many tissues and organs, butprincipally attacks the joints producing a inflammatory synovitis thatoften progresses to destruction of the articular cartilage and ankylosisof the joints. Rheumatoid arthritis can also produce diffuseinflammation in the lungs, pericardium, pleura, and sclera, and alsonodular lesions, most common in subcutaneous tissue under the skin.Although the cause of rheumatoid arthritis is unknown, autoimmunityplays a pivotal role in its chronicity and progression.

Due to the ability of the conjugates described herein to be targeted tobodily sites characterized by angiogenesis the conjugates can be furtherutilized for monitoring the level of angiogenesis within a body of apatient. The method according to these embodiments of the invention iseffected by administering to the subject any of the conjugates describedherein, having a labeling agent attached to the polymer, as describedherein, and employing an imaging technique for monitoring a distributionof the conjugate within the body or a portion thereof.

For example, the level of angiogenesis in tumor sites can serve as ameasure of the size of a tumor as well as the level of metabolicactivity in the tumor cells.

Other examples of disease conditions in which the monitoring of thelevel of angiogenesis by the conjugates described herein may bebeneficial, are atherosclerosis, hypertension, rheumatoid arthritis,diabetes and diabetes related complications.

Accordingly, according to another aspect of some embodiments of thepresent invention there are provided uses of any of the conjugatesdescribed herein, having a labeling agent as described herein, asdiagnostic agents and/or in the manufacture of a diagnostic agent formonitoring a medical condition associated with angiogenesis.

According to another aspect of some embodiments of the presentinvention, each of the conjugates described herein, which comprises alabeling agent, is identified for use a diagnostic agent, for monitoringa medical condition associated with angiogenesis.

Suitable imaging techniques include but are not limited to positronemission tomography (PET), gamma-scintigraphy, magnetic resonanceimaging (MRI), functional magnetic resonance imaging (FMRI),magnetoencephalography (MEG), single photon emission computerizedtomography (SPECT) computed axial tomography (CAT) scans, ultrasound,fluoroscopy and conventional X-ray imaging. The choice of an appropriateimaging technique depends on the nature of the labeling agent, and iswithin the skill in the art. For example, if the labeling agentcomprises Gd ions, then the appropriate imaging technique is MRI; if thelabeling agent comprises radionuclides, an appropriate imaging techniqueis gamma-scintigraphy; if the labeling agent comprises an ultrasoundagent, ultrasound is the appropriate imaging technique, etc.

The conjugates described hereinabove may be administered or otherwiseutilized in this and other aspects of the present invention, either asis, or as a pharmaceutically acceptable salt, enantiomer, diastereomer,solvate, hydrate or a prodrug thereof.

The phrase “pharmaceutically acceptable salt” refers to a chargedspecies of the parent compound and its counter ion, which is typicallyused to modify the solubility characteristics of the parent compoundand/or to reduce any significant irritation to an organism by the parentcompound, while not abrogating the biological activity and properties ofthe administered compound. The neutral forms of the compounds arepreferably regenerated by contacting the salt with a base or acid andisolating the parent compound in a conventional manner. The parent formof the compound differs from the various salt forms in certain physicalproperties, such as solubility in polar solvents, but otherwise thesalts are equivalent to the parent form of the compound for the purposesof the present invention. The phrase “pharmaceutically acceptable salts”is meant to encompass salts of the active compounds which are preparedwith relatively nontoxic acids or bases, depending on the particularsubstituents found on the compounds described herein. When conjugates ofthe present invention contain relatively acidic functionalities, baseaddition salts can be obtained by contacting the neutral (i.e.,non-ionized) form of such conjugates with a sufficient amount of thedesired base, either neat or in a suitable inert solvent. Examples ofpharmaceutically acceptable base addition salts include sodium,potassium, calcium, ammonium, organic amino, or magnesium salt, or asimilar salt. When conjugates of the present invention containrelatively basic functionalities, acid addition salts can be obtained bycontacting the neutral form of such conjugates with a sufficient amountof the desired acid, either neat or in a suitable inert solvent.Examples of pharmaceutically acceptable acid addition salts includethose derived from inorganic acids like hydrochloric, hydrobromic,nitric, carbonic, monohydrogencarbonic, phosphoric,monohydrogenphosphoric, dihydrogenphosphoric, sulfuric,monohydrogensulfuric, hydriodic, or phosphorous acids and the like, aswell as the salts derived from relatively nontoxic organic acids likeacetic, propionic, isobutyric, maleic, malonic, benzoic, succinic,suberic, fumaric, lactic, mandelic, phthalic, benzenesulfonic,p-tolylsulfonic, citric, tartaric, methanesulfonic, and the like. Alsoincluded are salts of amino acids such as arginate and the like, andsalts of organic acids like glucuronic or galactunoric acids and thelike (see, for example, Berge et al., “Pharmaceutical Salts”, Journal ofPharmaceutical Science, 1977, 66, 1-19). Certain specific conjugates ofthe present invention contain both basic and acidic functionalities thatallow the conjugates to be converted into either base or acid additionsalts.

The neutral forms of the conjugates are preferably regenerated bycontacting the salt with a base or acid and isolating the parentconjugate in a conventional manner. The parent form of the conjugatediffers from the various salt forms in certain physical properties, suchas solubility in polar solvents, but otherwise the salts are equivalentto the parent form of the conjugate for the purposes of the presentinvention.

The term “prodrug” refers to an agent, which is converted into theactive compound (the active parent drug) in vivo. Prodrugs are typicallyuseful for facilitating the administration of the parent drug. Theprodrug may also have improved solubility as compared with the parentdrug in pharmaceutical compositions. Prodrugs are also often used toachieve a sustained release of the active compound in vivo.

The conjugates described herein may possess asymmetric carbon atoms(optical centers) or double bonds; the racemates, diastereomers,geometric isomers and individual isomers are encompassed within thescope of the present invention.

As used herein, the term “enantiomer” describes a stereoisomer of acompound that is superposable with respect to its counterpart only by acomplete inversion/reflection (mirror image) of each other. Enantiomersare said to have “handedness” since they refer to each other like theright and left hand. Enantiomers have identical chemical and physicalproperties except when present in an environment which by itself hashandedness, such as all living systems.

The conjugates described herein can exist in unsolvated forms as well assolvated forms, including hydrated forms. In general, the solvated formsare equivalent to unsolvated forms and are encompassed within the scopeof the present invention. Certain conjugates of the present inventionmay exist in multiple crystalline or amorphous forms. In general, allphysical forms are equivalent for the uses contemplated by the presentinvention and are intended to be within the scope of the presentinvention.

The term “solvate” refers to a complex of variable stoichiometry (e.g.,di-, tri-, tetra-, penta-, hexa-, and so on), which is formed by asolute (the conjugate described herein) and a solvent, whereby thesolvent does not interfere with the biological activity of the solute.Suitable solvents include, for example, ethanol, acetic acid and thelike.

The term “hydrate” refers to a solvate, as defined hereinabove, wherethe solvent is water.

According to another aspect of embodiments of the invention there isprovided a pharmaceutical composition comprising, as an activeingredient, any of the conjugates described herein and apharmaceutically acceptable carrier

Accordingly, in any of the methods and uses described herein, any of theconjugates described herein can be provided to an individual either perse, or as part of a pharmaceutical composition where it is mixed with apharmaceutically acceptable carrier.

As used herein a “pharmaceutical composition” refers to a preparation ofone or more of the conjugates described herein (as active ingredient),or physiologically acceptable salts or prodrugs thereof, with otherchemical components including but not limited to physiologicallysuitable carriers, excipients, lubricants, buffering agents,antibacterial agents, bulking agents (e.g. mannitol), antioxidants(e.g., ascorbic acid or sodium bisulfite), anti-inflammatory agents,anti-viral agents, chemotherapeutic agents, anti-histamines and thelike. The purpose of a pharmaceutical composition is to facilitateadministration of a compound to a subject. The term “active ingredient”refers to a compound, which is accountable for a biological effect.

The terms “physiologically acceptable carrier” and “pharmaceuticallyacceptable carrier” which may be interchangeably used refer to a carrieror a diluent that does not cause significant irritation to an organismand does not abrogate the biological activity and properties of theadministered compound.

Herein the term “excipient” refers to an inert substance added to apharmaceutical composition to further facilitate administration of adrug. Examples, without limitation, of excipients include calciumcarbonate, calcium phosphate, various sugars and types of starch,cellulose derivatives, gelatin, vegetable oils and polyethylene glycols.

Techniques for formulation and administration of drugs may be found in“Remington's Pharmaceutical Sciences” Mack Publishing Co., Easton, Pa.,latest edition, which is incorporated herein by reference.

Pharmaceutical compositions for use in accordance with the presentinvention thus may be formulated in conventional manner using one ormore pharmaceutically acceptable carriers comprising excipients andauxiliaries, which facilitate processing of the compounds intopreparations which can be used pharmaceutically. Proper formulation isdependent upon the route of administration chosen. The dosage may varydepending upon the dosage form employed and the route of administrationutilized. The exact formulation, route of administration and dosage canbe chosen by the individual physician in view of the patient's condition(see e.g., Fingl et al., 1975, in “The Pharmacological Basis ofTherapeutics”, Ch. 1 p. 1).

The pharmaceutical composition may be formulated for administration ineither one or more of routes depending on whether local or systemictreatment or administration is of choice, and on the area to be treated.Administration may be done orally, by inhalation, or parenterally, forexample by intravenous drip or intraperitoneal, subcutaneous,intramuscular or intravenous injection, or topically (includingophtalmically, vaginally, rectally, intranasally).

Formulations for topical administration may include but are not limitedto lotions, ointments, gels, creams, suppositories, drops, liquids,sprays and powders. Conventional pharmaceutical carriers, aqueous,powder or oily bases, thickeners and the like may be necessary ordesirable.

Compositions for oral administration include powders or granules,suspensions or solutions in water or non-aqueous media, sachets, pills,caplets, capsules or tablets. Thickeners, diluents, flavorings,dispersing aids, emulsifiers or binders may be desirable.

Formulations for parenteral administration may include, but are notlimited to, sterile solutions which may also contain buffers, diluentsand other suitable additives. Slow release compositions are envisagedfor treatment.

The amount of a composition to be administered will, of course, bedependent on the subject being treated, the severity of the affliction,the manner of administration, the judgment of the prescribing physician,etc.

The pharmaceutical composition may further comprise additionalpharmaceutically active or inactive agents such as, but not limited to,an anti-bacterial agent, an antioxidant, a buffering agent, a bulkingagent, a surfactant, an anti-inflammatory agent, an anti-viral agent, achemotherapeutic agent and an anti-histamine.

According to an embodiment of the present invention, the pharmaceuticalcomposition described hereinabove is packaged in a packaging materialand identified in print, in or on the packaging material, for use in thetreatment of a medical condition associated with angiogenesis.

According to another embodiment of the present invention, thepharmaceutical composition is packaged in a packaging material andidentified in print, in or on the packaging material, for use inmonitoring a medical condition associated with angiogenesis.

Compositions of the present invention may, if desired, be presented in apack or dispenser device, such as an FDA approved kit, which may containone or more unit dosage forms containing the active ingredient. The packmay, for example, comprise metal or plastic foil, such as a blisterpack. The pack or dispenser device may be accompanied by instructionsfor administration. The pack or dispenser may also be accommodated by anotice associated with the container in a form prescribed by agovernmental agency regulating the manufacture, use or sale ofpharmaceuticals, which notice is reflective of approval by the agency ofthe form of the compositions or human or veterinary administration. Suchnotice, for example, may be of labeling approved by the U.S. Food andDrug Administration for prescription drugs or of an approved productinsert.

While reducing the present invention to practice, the present inventorshave designed and successfully practiced a novel process for conjugatingto polymer a therapeutically active agent, an angiogenesis targetingmoiety and optionally a labeling agent. It is noted that synthesizingsuch a polymeric conjugate is subjected to various limitations, imposedby a different solubility of the moieties to be conjugates, complicateddesired structural features that are required for optimal performance ofthe conjugate, incompatibility of the reactants, and the like. Hence,devising a process that overcomes these limitations and is designed toobtain a conjugate that exhibits at least a reasonable performance, ishighly advantageous.

According to another aspect of embodiments of the invention, there isprovided a process of preparing the conjugates described herein. Theprocess is effected by:

(a) co-polymerizing a plurality of monomeric units that form thepolymeric backbone, at least one of the monomeric units terminating by afirst reactive group, and at least one of the monomeric unitsterminating by a second reactive group, to thereby obtain a co-polymerthat comprises a plurality of backbone units, at least one backbone unithaving the first reactive group and at least one backbone unit havingthe second reactive group, said first reactive group being capable ofreacting with the angiogenesis targeting moiety and the second reactivebeing capable of reacting with the therapeutically active agent;

(b) reacting the co-polymer with the angiogenesis targeting moiety or aderivative thereof, via the first reactive group, to thereby obtain acopolymer having the angiogenesis targeting moiety attached to apolymeric backbone thereof; and

(c) further reacting the co-polymer with the therapeutically activeagent or a derivative thereof, via the second reactive group, to therebyobtain the co-polymer having the therapeutically active agent attachedto a polymeric backbone thereof,

thereby obtaining the conjugate.

In some embodiment, (b) is performed subsequent to, concomitant with orprior to (c). Thus, the process may be effected such that thetherapeutically active agent is first reacted with the functionalizedpolymeric backbone, thereby obtaining the polymeric backbone having thetherapeutically active agent attached thereto and then the angiogenesistargeting moiety is reacted with the functionalized polymeric backbonethereby obtaining the conjugate.

The copolymerization can be effected by any polymerization method knownin the art.

In some embodiments, the at least one monomeric unit that terminateswith the first reactive group comprises a first plurality of themonomeric units.

In some embodiments, the at least one monomeric unit that terminateswith the second reactive group comprises a second plurality of themonomeric units.

The monomeric units described herein, which terminate by a reactivegroup, are also referred to herein as functionalized monomers orfunctionalized monomeric units.

The co-polymer formed by the co-polymerization is also referred toherein as a functionalized co-polymer or a functionalized polymericbackbone.

In some embodiments, the co-polymerization can be effected in thepresence of monomeric units which form the polymeric backbone, and whichare non-functionalized.

Each of the first and second reactive groups can be protected prior tothe respective conjugation thereto. In such cases, the process furthercomprises deprotecting the reactive group prior to the respectiveconjugation.

This allows a regio-controlled conjugation of, for example, thetherapeutically active agent to those backbone units that comprises abiodegradable linker.

As used herein, a “reactive group” describes a chemical group that iscapable of reacting with another group so as to form a chemical bond,typically a covalent bond. Optionally, an ionic or coordinative bond isformed.

A reactive group is termed as such if being chemically compatible with areactive group of an agent or moiety that should be desirably attachedthereto. For example, a carboxylic group is a reactive group suitablefor conjugating an agent or a moiety that terminates with an aminegroup, and vice versa.

Other exemplary reactive groups include, but are not limited to,hydroxy, nitro, halo, haloalkyl, carboxylates, thiol, thiocarboxylates,and the like.

A reactive group can be inherently present in the monomeric units of thepolymer and/or angiogenesis targeting moiety and the therapeuticallyactive agent, or be generated therewithin by terms of chemicalmodifications of the chemical groups thereon or by means of attaching tothese chemical groups a spacer or a linker that terminates with thedesired reactive group.

A discussed hereinabove, the conjugates described herein are designed soas to release the therapeutically active agent and angiogenesistargeting moiety in the desired bodily site (i.e. sites of extensiveangiogenesis). Thus, the therapeutically active agent and angiogenesistargeting moiety are linked to the polymer via a direct linkage or viaan indirect linkage, through a linker group, whereby, in someembodiments, the direct/indirect linkage is designed as being cleavableat conditions characterizing the desired bodily site (e.g., by certainenzymes or pH).

For example, when the polymer is polyglutamic acid (PGA), the processmay include the attachment of the therapeutically active agent andangiogenesis targeting moiety directly to the carboxylic groups of theglutamate amino acids.

Alternatively, the process may include the use of a linker as describedherein whereby the linker is attached to the monomeric units, prior toco-polymerizing, so as to obtain a polymeric backbone in which a portionof the backbone units have the linker attached thereto. Furtheralternatively, the linker can be attached to the reactive groups in thefunctionalized polymeric backbone. Optionally, the linkers may beattached first to the therapeutically active agent and/or theangiogenesis targeting moiety and then be attached to the respectivereactive group in the functionalized polymeric backbone. The linkerattaching the therapeutically active agent and the linker attaching theangiogenesis targeting moiety may be the same or different.

Hence, in some embodiments, the process described herein, is such thatat least one of the monomer unit of (a) comprises a linker as describedherein, wherein the linker terminates with a reactive group and whereinthe angiogenesis targeting moiety is linked to the polymer via thelinker.

In some embodiments, the process described herein, is such that at leastone of the monomer unit of (a) comprises a linker as described hereinwherein the linker terminates with a reactive group and wherein thetherapeutically active agent is linked to the polymer via the linker.Preferably, the process described herein, is such that the angiogenesistargeting moiety is also linked to the polymer via the linker asdescribed herein.

Optionally, the process may include attachment of a spacer as describedherein to the backbone units of the polymer and then to therapeuticallyactive agent and/or angiogenesis targeting moiety. Alternatively, thespacer may be attached first to the therapeutically active agent and/orto the angiogenesis targeting moiety and then to the polymer.

Thus, in the case of the polymer being PGA, the process may be effected,for example, by the attachment of a spacer (such as, for example,NH₂(CH₂)₂NH₂) to the therapeutically active agent and/or angiogenesistargeting moiety followed by attaching the spacer to the carboxylicgroups of the glutamate amino acids (for example, by attaching the aminegroup of the spacer to the carboxylic group of the PGA thereby obtainingan amide bond).

It should be appreciated that the spacers and linkers utilized forcoupling the therapeutically active agent and/or the angiogenesistargeting moiety to the polymer are designed so as to allow a smooth andefficient conjugation of the respective moiety and an optimalperformance of the obtained conjugate, as discussed elaboratelyhereinabove.

In the case of the polymer and/or the therapeutically active agentand/or the angiogenesis targeting moiety further comprising a linker theprocess of synthesis may include attaching the spacer to the linkermoiety rather than directly to polymer/agent/moiety comprising thelinker.

Generally, the therapeutically active agent or angiogenesis targetingmoiety can be attached to the monomeric units of the polymer, or to thebackbone units of the copolymer, by means of a functional group that isalready present in the native molecule and/or the backbone units of thepolymer or otherwise can be introduced by well-known procedures insynthetic organic chemistry without altering the activity of the agent.For example, the angiogenesis targeting moiety and the therapeuticallyactive agent can be attached to the polymer via an amide bond betweenthe terminal carboxylic group of a peptidic linker and an amine grouplocated in the angiogenesis targeting moiety and/or the therapeuticallyactive agent.

In some embodiments the process further comprises attaching a labelingagent, as defined herein, to the formed conjugate. The labeling agentcan be attached to either of functionalized monomeric units, prior toco-polymerization or to the formed co-polymer.

In some embodiments, the labeling agent is attached to the co-polymerconcomitantly with the angiogenesis targeting moiety. Alternatively, itis attached prior to or subsequent to attaching the angiogenesistargeting moiety and/or the therapeutically active agent.

In some embodiments, the process comprises co-polymerizing, along withthe functionalized and non-functionalized monomeric units describedherein, monomeric units terminating with a third reactive group, thethird reactive group being for conjugating thereto a labeling agent orany other additional moiety, as described herein.

Thus, each of the conjugates described in any of the embodiments of theinvention, may further include an additional moiety conjugated thereto.Such an additional moiety can be conjugated either to monomeric unitswithin and throughout the polymeric backbone, or be attached at one orboth ends of the polymeric backbone.

Such an additional moiety can be a labeling agent, as described herein,or an additional targeting moiety or an additional therapeuticallyactive agent, which may improve the performance of the formed conjugate.Such an additional moiety can further be a moiety that improves thesolubility, bioavailability and/or any other desired feature of theformed conjugate

As used herein the term “about” refers to ±10%.

The terms “comprises”, “comprising”, “includes”, “including”, “having”and their conjugates mean “including but not limited to”.

The term “consisting of means “including and limited to”.

The term “consisting essentially of” means that the composition, methodor structure may include additional ingredients, steps and/or parts, butonly if the additional ingredients, steps and/or parts do not materiallyalter the basic and novel characteristics of the claimed composition,method or structure.

As used herein, the singular form “a”, an and the include pluralreferences unless the context clearly dictates otherwise. For example,the term “a compound” or “at least one compound” may include a pluralityof compounds, including mixtures thereof.

Throughout this application, various embodiments of this invention maybe presented in a range format. It should be understood that thedescription in range format is merely for convenience and brevity andshould not be construed as an inflexible limitation on the scope of theinvention. Accordingly, the description of a range should be consideredto have specifically disclosed all the possible subranges as well asindividual numerical values within that range. For example, descriptionof a range such as from 1 to 6 should be considered to have specificallydisclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numberswithin that range, for example, 1, 2, 3, 4, 5, and 6. This appliesregardless of the breadth of the range.

Whenever a numerical range is indicated herein, it is meant to includeany cited numeral (fractional or integral) within the indicated range.The phrases “ranging/ranges between” a first indicate number and asecond indicate number and “ranging/ranges from” a first indicate number“to” a second indicate number are used herein interchangeably and aremeant to include the first and second indicated numbers and all thefractional and integral numerals therebetween.

It is appreciated that certain features of the invention, which are, forclarity, described in the context of separate embodiments, may also beprovided in combination in a single embodiment. Conversely, variousfeatures of the invention, which are, for brevity, described in thecontext of a single embodiment, may also be provided separately or inany suitable subcombination or as suitable in any other describedembodiment of the invention. Certain features described in the contextof various embodiments are not to be considered essential features ofthose embodiments, unless the embodiment is inoperative without thoseelements.

Various embodiments and aspects of the present invention as delineatedhereinabove and as claimed in the claims section below find experimentalsupport in the following examples.

EXAMPLES

Reference is now made to the following examples, which together with theabove descriptions, illustrate the invention in a non limiting fashion.

Materials and Methods General:

All reactions requiring anhydrous conditions were performed under anargon or nitrogen atmosphere.

Chemicals and solvents are either A.R. grade or purified by standardtechniques.

Thin layer chromatography (TLC): silica gel plates Merck 60 F₂₅₄;compounds were visualized by irradiation with UV light and/or bytreatment with a solution of phosphomolybdic acid (20% wt. in ethanol)or ninhydrine (10% wt. ethanol), followed by heating.

Size Exclusion chromatography (SEC): Shephadex G25 resin, eluent H₂O.SEC analysis was performed using a Viscotek TDA™ Triple detector system,with two TSK-gel columns in series (G3000 PWXL and G2500 PWXL) and aguard column (PWXL Guardcol). A flow rate of 0.8 ml/min, and a mobilephase 0.1 M PBS buffer was used. Viscotek Instrument software wasemployed for data analysis. HPLC was performed using Merck HitachiL-2130 HPLC pump and L-2200 autosampler with a Lichrospher® 100 C18(150×3.9 mm) column, and as mobile phase different acetonitrilegradients in aqueous 0.1% TFA. The UV spectra were recorded on a JascoV-530 UV/Vis spectrophotometer.

Flash chromatography (FC): silica gel Merck 60 (particle size0.040-0.063 mm), eluent given in parentheses.

¹H NMR: Bruker AMX 200 or 400 instrument. The chemical shifts areexpressed in δ relative to TMS (δ=0 ppm) and the coupling constants J inHz. The spectra are recorded in CDCl₃, as a solvent at room temp.

400 Mesh copper grid SPI Supplies, West Chester, Pa.

All chemical reagents including N,N-Diisopropylcarbodiimide (DIC),1-hydroxybenzotriazol (HOBt), di-isopropylethylamine (DIEA),N-hydroxysuccinimide (OHSuc), N,N′-dimethylaminopyridine (DMAP) andanhydrous dimethylformamide (DMF) were purchased from Sigma-AldrichQuímica S.A. (Madrid, Spain) and used without further purification.

All solvents were of HPLC grade and were obtained from Merck (Barcelona,Spain). Paclitaxel was purchased from Petrus Chemicals and Materials Ltd(Israel). E-[c(RGDfk)₂] (SEQ ID NO: 26) and c(RADfk) (SEQ ID NO:40) werepurchased from Peptides International, Louisville, Ky., USA. c(RGDfk)(SEQ ID NO:9) was obtained from Matthias Barz and Prof. Dr. R. Zentel(University of Mainz, Germany). Fibronectin was purchased fromBiological Industries Ltd (Beit Haemek, Israel). Fibrinogen was fromSigma-Aldrich (Israel). Fluorescence dye Oregon green cadaverine wasfrom Molecular Probes. All other reagents were of general laboratorygrade and were purchased from Merck unless otherwise stated.

Anti-ERK1/2 MAPK, P-ERK1/2 MAPK, AKT and P-AKT^(Ser473) antibodies arepurchased from Cell Signaling Technology Ltd. Bax, anti-cleaved PARP,caspase-3 and caspase-9 are purchased from Cell Signaling TechnologyLtd.

Ethics Statement:

All animal procedures were performed in compliance with Tel AvivUniversity, Sackler School of Medicine guidelines and protocols approvedby the Institutional Animal Care and Use Committee. Body weight andtumor size were measured three times a week.

Cell Culture:

U87 human glioblastoma and MG-63-Ras human osteosarcoma cells wereobtained from the American Type Culture Collection (ATCC # HTB-14).MG-63-Ras cells were transfected with activated ras (MG-63-Ras) aspreviously described [Segal, et al 2009 PLoS ONE, 4: e5233,] in order togenerate an in vivo fast-growing tumor cell line. mCherry-labeledMG-63-Ras human osteosarcoma cell line and mCherry-labeled U87 humanglioblastoma were obtained by infection with a pQC-mCherry retroviralvector as previously described [Segal et al. 2009, PloS ONE 4:e5233].The infected cells were selected for stable expression of mCherry usingpuromycin.

PANC02 murine pancreatic tumor cells were established by Corbett et al.Cancer Res. 1984 44: 717-726 and were cultured in Dulbecco's modifiedEagle's medium (DMEM) supplemented with 10% fetal bovine serum (FBS),100 mg/ml Penicillin, 100 U/ml Streptomycin, 12.5 U/ml Nystatin, 2 mML-glutamin, 1 mM Sodium Pyruvate and MEM-EAGLE non-essential amino acids(Biological Industries, Israel).

Human umbilical vein endothelial cells (HUVEC) were purchased fromLonza, Switzerland. Cells were cultured in Endothelial Growth Medium-2(EGM-2) (Cambrex, USA). MCF7/Cyr61 cells were cultured in Dulbecco'smodified Eagles' Medium (DMEM) supplemented with 10% Fetal Bovine Serum(FBS).

All cells were grown at 37° C.; 5% CO₂.

Luciferase Infection of M7/Cyr61 Cell Line:

In order to generate a stable luciferase-expressing MCF-7/Cyr61 cellline (overexpressing the protein CYR61 and havingPaclitaxel-resistance), MCF7/Cyr61 cells are transfected with a pBaberetroviral vector carrying the firefly luciferase gene and tested bothin vitro and in vivo using a Biospace Photon Imager following thebioluminescence in a whole animal imaging system. For comparison,control MCF-7 cells not expressing CYR61 and thus not havingPaclitaxel-resistance, are also transfected with the firefly luciferasegene or mCherry.

Western Blot:

For evaluation of the level of expression of proteins, cells areharvested with Phosphate Buffered Saline (PBS containing 0.25 mM EDTAand lysed in 20 mM Tris, 150 mM NaCl, 1% Triton X-100, pH 7.5,supplemented with protease inhibitors (Complete™ solution,Boehringer-Manheim) and 2 mM Na₃VO₄. The cell debris is pelleted and theprotein concentration determined in the supernatant using the BCAreagent (Pierce). Proteins are separated by SDS-PAGE, transferred to anitrocellulose membrane, and immunoblotted for 2 hours with the relevantprimary antibodies. Following Tris-Buffered Saline Tween (TBS-T) washes,peroxidase-conjugated IgG (Jackson) is added, the membrane washed againwith TBS-T and immunoreactive bands is detected by West PicoChemiluminescent Substrate (Pierce).

Flow Cytometry Analysis:

For evaluation of the level of apoptosis in a cell culture, followingdifferent treatments with PGA copolymer-c(RGDfk)₂-Paclitaxel (SEQ IDNO:18) and HPMA copolymer-c(RGDfk)₂-Paclitaxel (SEQ ID NO:23),representative conjugates according to the embodiments of the presentinvention, cells are harvested, fixed with methanol, and re-suspended inPBS. The fluorescent marker, Propidium iodide (50 μg/ml) is added fornuclear staining and the cells are analyzed in a fluorescence-activatedcell sorter (FACS unit, Inter-departmental Facilities, Faculty ofMedicine, Tel Aviv University).

Cell Proliferation Assay:

The anti-angiogenesis and anti-proliferative activity of the conjugatesdescribed herein was evaluated by the effect of the conjugates on theproliferation of HUVEC, U87 and PANC02 cells.

HUVEC were plated onto 24-well plate (1×10⁴ cells/well) in endothelialcell basal medium 2 (EBM-2; Cambrex, USA) supplemented with 5% fetalbovine serum (FBS). Following 24 hours of incubation (37° C.; 5% CO₂)medium was replaced with Endothelial cell growth medium-2 (EGM-2;Cambrex, USA). U87 and PANC02 cells were plated onto 96 well plate(2×10³ cells/well) in DMEM supplemented with 5% FBS and incubated for 24hours (37° C.; 5% CO₂). Following 24 hours of incubation the medium wasreplaced with DMEM containing 10% FBS. Cells were challenged with thetested compounds at serial concentrations for 72 hours. After incubationthe number of HUVEC were counted by Coulter Counter and U87, and PANC02cells were counted by XTT respectively.

αvβ3 Expression Detection:

HUVEC, U87 and Panc02 were harvested with PBS containing 2.5 mM EDTA,followed by re-suspension of the cells in serum free medium (EBM-2 forHUVEC and DMEM for U87 and Panc02) and incubation for 30 minutes. Thecells were divided and further re-suspended in PBS containing Mg²⁺andCa²⁺. The cells were then incubated together with the primary antibodyMAB1976-anti αvβ₃ integrin (Chemicon, 1:20) for 30 minutes, at roomtemperature, in gentle rocking. Serving as control were cells notincubated with any antibody. Then, the cells were washed andre-suspended in PBS with the second antibody anti mouse-FITC (Jackson,1:50) and incubated in the dark for 30 minutes, at room temperature, ingentle rocking. The cells (1×10⁵) were collected byFluorescence-activated cell sorter (FACS), and statistical analysis wasperformed using WinMDI software.

αvβ3 Interaction with Fluorescently Labeled Conjugates:

A fluorescence probe, Oregon Green-cadaverine (OG), was conjugated toPGA conjugates through the free carboxylic groups (see Example 5 forsynthesis description), in order to study the cellular uptake andtrafficking.

HUVEC were plated onto 6 mm plates (5×10⁵ cells/plate) in EBM-2(Cambrex, USA) supplemented with 5% FBS. Following 24 hours ofincubation (37° C.; 5% CO₂), cells were challenged with either PGA-OG,PGA-c(RADfk)-OG (SEQ ID NO: 24) or PGA-E-[c(RGDfk)_(2])-OG (SEQ IDNO:25) diluted in EGM-2 medium for 5, 10, 15, 30 or 60 minutes. Cellswere then washed in PBS (X3), harvested with PBS containing 2.5 mM EDTAand analyzed with the ImageStream 100 imaging flow cytometer (Amnis).Analysis was performed using IDEAS software.

Capillary-Like Tube Formation Assay:

The anti-angiogenesis activity of the conjugates was evaluated by theeffect of the conjugates on the ability of HUVEC cells to formcapillary-like tube structures.

The surface of 24-well plates was coated with Matrigel matrix (50μl/well) (BD Biosciences, USA) on ice and was then allowed to polymerizeat 37° C. for 30 minutes. HUVEC (3×10⁴ cells) were challenged with thetested compounds, and were seeded on coated plates in the presence ofcomplete EGM-2 medium. After 8 hours of incubation (37° C.; 5% CO₂),wells were imaged using Nikon TE2000E inverted microscope integratedwith Nikon DS5 cooled CCD camera by 4× objective, brightfield technique.During the tube formation assay endothelial cells directionally migrateto align, branch and form polygonal networks (i.e. tube likestructures). The extent of capillary-like tube structures is inverselyproportional to the anti-angiogenesis activity of the compounds.

Migration Assay:

The anti-angiogenesis activity of the conjugates was evaluated byexamining the effect of the conjugates on the ability of HUVEC tomigrate toward the Vascular Endothelial Growth Factor (VEGF).

Cell migration assay was performed using modified 8 μm Boyden chambersTranswells® (Costar Inc., USA) coated with 10 μg/ml fibronectin HUVEC(15×10⁴ cells/100 μl) were challenged with the tested compounds thatwere added to the upper chamber of the transwells for 2 hours. Followingincubation, cells were allowed to migrate to the underside of thechamber for 4 hours in the presence or absence of VEGF (20 ng/ml) in thelower chamber. Cells were then fixed and stained (Hema 3 Stain System;Fisher Diagnostics, USA). The stained migrated cells were imaged usingNikon TE2000E inverted microscope integrated with Nikon DS5 cooled CCDcamera by 10× objective, brightfield illumination. Migrated cells fromthe captured images per membrane were counted using NIH image software.Migration was normalized to the percent of migration toward VEGF ofHUVEC which were not incubated with any compound. The extent ofmigration is inversely proportional to the anti-angiogenesis activity ofthe compounds.

Endothelial Cell Adhesion Assay:

The ability of E-[c(RGDfk)₂] and E-c(RGDfk) moieties (SEQ ID NOs: 2 and41) in the conjugates to inhibit endothelial attachment to cellularmatrix after conjugation, was assessed using an adhesion assay. Flatbottom 96-well culture plates (Nunc, Denmark) were coated with 0.5μg/well fibrinogen overnight at 4° C. After washing three times withPhosphate buffered saline (PBS), the wells were blocked with 1% bovineserum albumin (BSA) for 1 hour at 37° C. and washed three times againwith PBS. HUVEC were harvested in phosphate-buffered saline (137 mMNaCl, 2.7 mM KCl, 4.3 mM Na2HPO4, 1.4 mM KH₂PO₄, pH 7.3) with 2.5 mMEDTA and resuspended in EBM-2 serum-free media (Clonetics). HUVEC wereincubated for 30 minutes, at room temperature, with the testedcompounds. The treated HUVEC were plated at 5×10⁴ cells per well andwere allowed to attach for 1 hour at 37° C. After incubation, theunattached cells were removed by rinsing the wells with PBS. Theattached cells were fixed with 3.7% formaldehyde, stained with 0.5%crystal violet and were imaged using Nikon TE2000E inverted microscopeintegrated with Nikon DS5 cooled CCD camera by 4× objective, brightfieldtechnique. The number of attached cells was quantified with NIH ImageJprocessing and analysis software. Non-specific binding was determined byadhesion of HUVEC cells, which were not incubated with any of the testedcompounds, to BSA-coated plates.

Determination of % of Free Paclitaxel and Free Peptide in the ConjugatesSynthesized:

In order to determine the free Paclitaxel (PTX) and free peptide [eitherc(RGDfk)₂ (SEQ ID NO: 26) or c(RGDfk) (SEQ ID NO: 9) or control freec(RADfk)] (SEQ ID NO:40) content in the conjugates synthesized, aqueoussolutions of the conjugates (1 mg/ml) were prepared, and an aliquot (100pd) from each conjugate solution was added to a polypropylene tubefollowed by the addition of water up to a volume of 1 ml. Then, 5 ml ofCHCl₃ and 2-propanol at a ratio of 4:1 was added and the aliquot sampleswere thoroughly extracted by vortexing (3×10 seconds). The upper aqueouslayer was carefully removed and the solvent evaporated under N₂. The dryresidue was dissolved in 200 μl of HPLC grade methanol.

A similar procedure was carried out for the free compound (PTX orpeptide) (in which case a aliquots of 200 μl from a 1 mg/ml solution ofthe compounds was added to polypropylene tubes). Addition of 1 ml ofMeOH to redissolve the product gave a 200 μg/ml stock from which a rangeof concentrations was prepared (2 to 100 μg/ml).

Alternatively, the aliquot of the conjugates solution as well as thefree compound solution were purified by a pre-made RP column with a C18Porous 50 resin using a mixture of MeOH:AcCN as the eluents. The solventwas then evaporated under N_(2(g)). The dry residue was then dissolvedin 200 μl of HPLC grade methanol.

The free amount of drug in the conjugates was determined by HPLC using aLichrospher® C18 (150×3.9 mm) column. Flow rate of 1 ml/min using anacetonitrile gradient in aqueous 0.1% TFA (to simultaneously determinePTX and the peptide, a gradient from 10% to 90% of acetonitrile in 28min was used). The retention time was r.t.=16.9 minutes for PTX,r.t.=8.0 minutes for E-[c(RGDfk)₂] (SEQ ID NO: 2) and r.t.=5.3 minutesfor c(RADfk) (SEQ ID NO:40) and r.t.=5.7 minutes for c(RGDfk) (SEQ IDNO: 9)=220 nm).

Quantitative Evaluation of PGA Conjugates Hydrodynamic Diameter and SizeDistribution:

The mean hydrodynamic diameter of the PGA conjugates was evaluated usinga real time particle analyzer (NanoSight LM20™) containing asolid-state, single mode laser diode (<20 mW, 655 nm) configured tolaunch a finely focused beam through a 500 μl sample chamber. The testedconjugate was dissolved in PBS to a final concentrations of 9.9 mg/ml.The samples were then injected into the chamber by syringe and allowedto equilibrate to a unit temperature (23° C.) for 30 seconds. Theparticles dynamics were visualized at 30 frames per second (fps) for 60seconds at 640×480 resolution by the device CCD camera. The paths theparticles take under Brownian motion over time were analyzed usingNanoparticle Tracking Analysis (NTA) software. The diffusion coefficientand hence sphere equivalent hydrodynamic radius of each particle wasseparately determined and the particle size distribution profiles weregenerated. Each sample was measured three times in triplicates, and theresults represent the mean diameter.

Release of PTX from PGA Copolymer -E−C(RGDfk)₂-Paclitaxel Conjugate (SEQId NO:18) in the Presence of Cathepsin B:

The ability of Cathepsin B to cleave and therefore release PTX from PGAcopolymer-E−c(RGDfk)₂-PTX (SEQ ID NO:18) was assessed as follows:

Cathepsin B (5 U) was added last to a 1 ml solutions containing 3 mg ofthe tested conjugates and 20 mM sodium acetate, 2 mM EDTA and 5 mM DTTat a pH of 6 and at a temperature of 37° C. Solutions containing freePGA polymer and free PTX served as control. Sample aliquots (100 μl)were taken at various time points up to 72 hours, frozen and stored inliquid nitrogen, until assayed by HPLC (by Porous 50 resin) and/or byGel permeation chromatography (GPC; direct analysis of 50 μl aliquots).PGA polymer incubated in buffer alone (without addition of cathepsin B)served as an additional control to assess non-enzymatic hydrolyticcleavage. The amount of free PTX released from the tested compounds wasassessed by HPLC=220 nm). Doxycycline was used as internal standard inall cases. In addition, an LC-MS analysis of the released compounds wasalso carried out to in order determine the major metabolites released.The MW of the conjugates was determined by diluting 50 pd aliquots ofthe conjugate containing solution to a final volume of 200 μl with PBSbuffer and subjecting the aliquots to GPC analysis (Viscotek TDAdetector).

Stability of the Conjugates in Plasma:

Stability in plasma was assessed by incubating each of the conjugates (3mg/ml), for 24 hours, at 37° C., in plasma freshly extracted from Wistarrats. At various time points, samples of 100 μl were collected. 15 μl of0.2 mg/ml solution of doxycycline in MeOH served as an internalstandard, and 135 μl of a mixture of MeCN:MeOH 50:50 with 2% ZnSO₄ wereadded to each sample in order to precipitate serum proteins. The sampleswere centrifuged at 14000 rpm for 5 minutes, and 150 μl of thesupernatant were subjected to analysis by HPLC as described hereinabove.The amount of PTX release from the conjugates in the presence of serumwas determined to be insignificant.

αvβ3 Interaction with E-[c(RGDfk)₂] in vivo:

SCID male were inoculated s.c. with 2×10⁶ mCherry-labeled U87 humanosteosarcoma or with 5×10⁶ mCherry-labeled MG-63 human osteosarcoma.Mice bearing an average volume of 175 mm³ U87 human osteosarcoma tumorswere injected i.v. with PGA-E-[c(RGDfk)₂]-OG (SEQ ID NO: 25; 50 μM-RGD)or PGA-c(RADfk)-OG (SEQ ID NO: 24; 50 μM-RGD-equivalent dose) (n=3mice/group). One hour after injection, tumors were removed, dissected tothin slices and examined under Zeiss Meta LSM 510 confocal imagingsystem.

Mice bearing 600 mm³ MG-63 human osteosarcoma tumors were injected i.v.with PGA-PTX−E-[c(RGDfk)₂]-OG (SEQ ID NO: 25; 50 μM-RGD), PGA-PTX-OG orPGA-PTX−c(RADfk)-OG (SEQ ID NO: 24; 50 μM-RGD-equivalent dose) (n=3mice/group). 30 and 60 min after injection, tumors were removed washedseveral times with cold PBS, fixed with 3.5% paraformaldehyde for 15minutes at RT and washed with PBS again.

Tumors were then homogenized and analyzed with the ImageStream 100(amnis). Analysis was performed using IDEAS software.

Confocal Microscopy:

Cellular colocalization of OG labeled PGA-E-[c(RGDfk)₂] (SEQ ID NO: 25)conjugate was monitored utilizing a Zeiss Meta LSM 510 confocal imagingsystems with 40oil objectives. All images were taken using a multi-trackchannel acquisition to prevent emission cross-talk between fluorescentdyes. Single XY, XZ plane-images were acquired in 1024×1024 resolution.

Statistical Methods:

Data are expressed as mean±SD. Statistical significance was determentusing an unpaired t-test. P<0.05 was considered statisticallysignificant. All statistical tests are two-sided.

Example 1 Synthesis of HPMA copolymer-E-c(RGDfk)₂-Paclitaxel (SEQ ID NO:23)

The general synthesis of an HPMA copolymer-c(RGDfk)₂-Paclitaxel (SEQ IDNO:23) (Compound 2) is depicted in FIG. 6.

As shown in FIG. 6, the HPMA-c(RDGfk)₂-Paclitaxel conjugate (SEQ IDNO:23) is prepared in a two-step synthesis, as follows: The peptidelinker, Gly-Phe-Leu-Gly (SEQ ID NO:10) is a cathepsin B-cleavablelinker. Cathepsin B is a lysosomal enzyme overexpressed in bothepithelial and endothelial tumor cells. First, the conjugation ofc(RDGfk)₂ (SEQ ID NO:26) to HPMA copolymer-Gly-Phe-Leu-Gly (SEQ IDNO:42) by non-specific aminolysis using the amino group of the lysine iseffected. Next, the conjugation of Paclitaxel to the polymer through anester bond is effected. HPMA copolymer-Gly-Phe-Leu-Gly (GFLG 10 mol%)-p-nitrophenol (ONp) (SEQ ID NO:43) is used as multivalent polymericprecursor, therefore a maximum of 10 mol % functionalization is allowed.In order to keep an appropriate Paclitaxel loading a maximum of 5 mol %,c(RDGfk)₂ (SEQ ID NO:26) loading is considered.

Synthesis of HPMA-E-c(RDGfk)₂ (SEQ ID NO:44) (Compound 1):

HPMA copolymer-Gly-Phe-Leu-Gly-ONp (SEQ ID NO:43) is dissolved inanhydrous Dimethylformamide (DMF) under nitrogen atmosphere. c(RDGfk)₂(SEQ ID NO:26) is conjugated through aminolysis to the HPMAcopolymer-Gly-Phe-Leu-Gly-ONp (SEQ ID NO:43) in DMF and then mixedtogether. c(RDGfk)₂TFA (SEQ ID NO 45) in anhydrous DMF is then addedtogether with TEA. The reaction is allowed to proceed for 8 hours atroom temperature. TLC is used to monitor the reaction. The solvent isthereafter removed under high vacuum and the conjugate is purified bysize exclusion chromatography (SEC), Sephadex LH-20 using methanol asmobile phase. For further purification, the conjugate is redissolved ina minimum amount of water, dialyzed and lyophilized yielding the desiredcompound 1 in a high percentage of purity. UV spectroscopy is used todetermine the peptide content of the conjugate. In order to characterizethe c(RDGfk)₂ loading (SEQ ID NO: 26) on the conjugates a calibrationcurve is carried out in DMF RT=25° C., at a maximum Absorbance of 266nm.

Synthesis of HPMA-copolymer-E-c(RDGfk)₂-Paclitaxel (SEQ ID NO:23)(Compound 2):

Paclitaxel is dissolved in DMF and added to the HPMA-c(RDGfk)₂ conjugate(SEQ ID NO:44) dissolved in DMF as well. The conjugate is re-purified,lyophilized and characterized by HPLC analysis at 254 nm.

The conjugate HPMA copolymer-TNP-470-RGD4C (SEQ ID NO:46) is similarlyprepared.

Example 2 Synthesis and Characterization of a PGACopolymer-E-c(RGDfk)₂-Paclitaxel Conjugate (SEQ ID NO:18) Synthesis ofPGA-Copolymer -E-c(RGDfk)₂-Paclitaxel Conjugate (SEQ ID NO:18)

The general synthesis of a PGA-E-[c(RGDfK)₂]-Paclitaxel (SEQ ID NO:18)(Compound 4) is depicted in FIG. 7. The ester linker is hydrolyticallylabile and PTX release is expected to occur under lysosomal acidic pH.The PGA-E-[c(RDGfk)₂]-Paclitaxel conjugate (SEQ ID NO:18) was preparedin two steps: first, the PTX was conjugated to the PGA polymer followedby the conjugation of the -E-[c(RDGfk)₂] peptide (SEQ ID NO:2) to thePTX−conjugated polymer. The ester linker between the carboxylic groupsof the glutamate monomeric units and the PTX as well as the [c(RDGfk)₂](SEQ ID NO: 26) are hydrolytically labile and under lysosomal acidic pHare cleaved thus releasing both PTX and -E-[c(RDGfk)_(2] (SEQ ID NO:)2).The peptide linkage between the glutamate monomeric units is ahydrolytically labile linker, which is also susceptible to cathepsinB-cleavage. The E-[c(RGDfK)₂] peptide (SEQ ID NO:2) was conjugated tothe PTX containing polymer through a glutamic acid (-E-) peptidiclinker.

PGA was used as a multivalent polymeric precursor. The starting PGA wassynthesized via N-Carboxyanhydride (NCA) polymerization of glutamicacid. Transition metal macroinitiators were used in order to overcomethe well-known limitations of conventional NCA polymerizations such asthe presence side-reactions that restrict control over MW and prohibitformation of well-defined block copolymers. The synthetic method wasperformed as previously described [Curtin et al. 1999, Journal of theAmerican Chemical Society 121: 7427-7428].

Synthesis of a PGA-Paclitaxel conjugate (Compound 3)

PTX was conjugated to the PGA (Mw 18,200, Mw/Mn 1.4) by carbodiimidecoupling. The reaction was allowed to proceed at room temperature for 24hours. Thin layer chromatography (TLC, silica) showed a completeconversion of the free PTX (R_(f)=0.6) to the PTX-polymer conjugate(Compound 3) (R_(f)=0, CH₂Cl₂/MeOH=90:10). The reaction was allowed toproceed at room temperature for 24 hours without product isolation.

Synthesis of PGA-Copolymer -E-c(RGDfk)₂-Paclitaxel (SEQ ID NO: 18)(Compound 4)

Following the completion of the PTX conjugation reactionN-hydroxysuccinimide (OHSuc) was added to the reaction mixture in orderto activate the remaining carboxylic groups of the glutamate monomersfor subsequent conjugation of the E-[c(RGDfK)₂] peptide (SEQ ID NO:2).The carboxylic group activation is important in order to avoidside-reactions (namely cross linking between two E-[c(RGDfK)₂] compounds(SEQ ID NO:2) via the carboxylic groups of their aspartic acids). Thereaction was allowed to proceed for 24 hours and was then stopped bypouring the reaction mixture into CHCl₃. The resulting precipitate wascollected and washed with acetone and MeOH in order to remove theunreacted OHSuc. The precipitate was further collected and dried undervacuum. CHCl₃ was kept to determine total drug loading (PTX) by HPLCthrough an indirect measurement. The solid intermediate was redissolvedin anhydrous DMF and E-[c(RGDfK)₂] peptide (SEQ ID NO:2) was conjugatedwith PGA through the -E-peptidic spacer using DMAP as a base catalyst.The reaction was allowed to proceed at room temperature for 72 hours andwas then stopped by pouring the reaction mixture into CHCl₃. Thin layerchromatography (TLC, silica) showed complete conversion of the freeE-[c(RGDfK)₂] (R_(f)=0.3) (SEQ ID NO:2) to the polymer conjugatedE-[c(RGDfK)₂] (SEQ ID NO: 18) (R_(f)=0, AcOH/MeOH=1:99). The resultingprecipitate was collected and dried in vacuum thus yielding the desiredCompound 4. CHCl₃ was kept to determine total drug loading E-[c(RGDfK)₂](SEQ ID NO:2) by HPLC through an indirect measurement.

The sodium salt of the PGA-PTX−E-[c(RGDfK)₂] (SEQ ID NO:47) conjugatewas obtained by dissolving the product in 1.0 M NaHCO₃ followed bypurification by SEC (Sephadex G25) in order to remove low molecularweight contaminants and salt excesses. Lyophilization of the purifiedfractions yielded the desired product as a white powder (70%-80% yield).

Synthesis of a Conjugate of PGA with a Single c(RGDfK) Moiety (SEQ IDNO:17)

PGA-RGDfk (SEQ ID NO:17; MW 200.37 g/mol) and the conjugatePGA-PTX-RGDfk (SEQ ID NO:19; MW 216.53 g/mol) were also similarlysynthesized and the % of drug loading is presented in Table 1. Thechemical structures of PGA-PTX-RGDfk conjugate (SEQ ID NO: 19) and theconjugate PGA-RGDfk (SEQ ID NO:17; are presented in FIGS. 2F and 2G,respectively.

Syntheses of “Control” Conjugates

For use as control compounds in the experiments described hereinbelow,other conjugates were also synthesized: PGA-PTX, PGA-c(RADfk) (SEQ IDNO:14), PGA-E-[c(RGDfk)₂] (SEQ ID NO:15) and PGA-PTX−c(RADfk) (SEQ IDNO:19). The chemical structures of PGA-PTX, PGA-c(RADfk) (SEQ ID NO:14)and PGA-E-[c(RGDfk)₂] (SEQ ID NO:15) conjugates is presented in FIGS.2C, 2D and 2E respectively. The chemical structure of PGA-PTX−c(RADfk)conjugate (SEQ ID NO:19) is presented in FIG. 3B.

Example 3 Synthesis of PGA-E-[c(RDGfk)₂] (SEQ ID NO:15; Compound 5)

As discussed hereinabove, PGA-E-[c(RGDfk)₂] (SEQ ID NO:15; is aconjugate used as a control in experiments described hereinbelow whichcompare the activity of the free [c(RGDfk)₂] (SEQ ID NO:26) and theconjugated [c(RGDfk)₂] peptide (SEQ ID NO:15). The general synthesis ofa PGA-E-[c(RGDfk)₂] (SEQ ID NO:15; Compound 5) is depicted in FIG. 8.

PGA was dissolved in anhydrous dimethylformamide (DMF) under nitrogenatmosphere and the glutamate carboxylic acids were activated usingOHSuc. The reaction was allowed to proceed for 24 hours. The resultantPGA-OSuc product was isolated by precipitation in CHCl₃ and washed withacetone and methanol.

E-[c(RGDfK)₂] (SEQ ID NO: 2) was then conjugated through thesuccinimidyl-activated esters to the PGA in DMF, as follows:E-[c(RGDfK)₂] (SEQ ID NO: 2) was added to the PGA-OSuc and the reactionwas allowed to proceed in DMF for 48 hours at room temperature. Thereaction was stopped by pouring the reaction mixture into CHCl₃. Thinlayer chromatography (TLC, silica) showed a complete conversion of thefree E-[c(RGDfK)₂] (SEQ ID NO: 2) (R_(f)=0.3) to the polymer conjugatedE-[c(RGDfK)₂] (SEQ ID NO: 15) (R_(f)=0, AcOH/MeOH=1:99). The resultingprecipitate was collected and dried under vacuum thus yielding thedesired Compound 5.

The sodium salt of the conjugate (SEQ ID NO:48) was obtained bydissolving the product in 1.0 M NaHCO₃, followed by purification by SEC(Sephadex G25) using water as mobile phase, in order to remove lowmolecular weight contaminants and salt excesses. Lyophilization of thepurified fractions yielded the desired product as a white powder(70%-80% yield).

Example 4 Characterization of Drug Loading, Hydrodynamic Diameter andEnzymatic Cleavage of the Conjugates Determination of PTX and of RGD- orRAD-Containing Moieties Loading

In order to keep an appropriate Paclitaxel loading, a maximum of 5 mol %E-[c(RGDfK)₂] (SEQ ID NO:2) loading was considered. The total PTXcontent in these polymeric conjugates was determined by UV (λ=227 nm and230 nm, calibration curve carried out at RT in MeOH) and HPLC (indirectanalysis wherein the PTX content in reaction residues at λ=220 nm, from35 to 80% of acetonitrile in 25 min, r.t.=10.8 minutes).

The total E-[c(RGDfK)₂] peptide (SEQ ID NO:2), E-c(RGDfK) peptide (SEQID NO:41) or control inactive peptide, E-c(RADfk) (SEQ ID NO:40) contentin these polymeric conjugates was determined by UV (λ=254 nm and 260 nm,calibration curve carried out at RT in MeOH), HPLC (indirect analysis ofpeptide content in reaction residues, flow rate 1 ml/minute using anacetonitrile gradient in aqueous 0.1% TFA from 5 to 75% of acetonitrilein 25 min, λ=220 nm, r.t.=7.9 minutes) and amino acid analysis (briefly,3 mg of each conjugate synthesized were hydrolyzed with 5N HCl at 160°C. for 4 hours, and samples were then lyophilized and sent to ParcCientific Barcelona (Barcelona, Spain) for analysis by LC-MS).

The % loading of PTX and the peptides in the synthesized conjugates ispresented in Table 1. Two PGA-PTX−E-[c(RGDfK)₂] conjugates (SEQ IDNO:18) were synthesized differing in the % loading of the PTX andE-[c(RGDfK)₂]. PTX was in the range of 2.6-5. mol % functionalizationand the % loading of E-[c(RGDfK)₂] peptide (SEQ ID NO: 2) was in therange of 3.9-5.7 mol % functionalization (the first conjugate had a5-4.7 mol % E-[c(RGDfk)₂] (SEQ ID NO: 2), and 2.6 mol % PTX loadings andthe second conjugate had a 3.9 mol % E-[c(RGDfk)₂] (SEQ ID NO: 2) and5.5 mol % PTX loadings) with a free drug content always less than 1.5 wt% of total drug.

TABLE 1 Total PTX Free drug content loading Total peptide(wt % of total drug)^(c) Conjugate (mol %) loading (mol %) PTX PeptidePGA-PTX 4.9 ± 0.3 ^(a) NA NA 1.2 ± 0.4 NA PGA-c(RADfk) NA 5.0 ± 0.3^(a)5.1 ± 0.1^(b) NA 0.9 ± 0.1 (SEQ ID NO: 14) PGA-c(RGDfk) NA 5.0 ± 0.3^(a)5.1 ± 0.1^(b) NA 1.0 ± 0.2 (SEQ ID NO: 17) PGA-E-[c(RGDfk)₂] NA 5.0 ±0.3^(a) 5.7 ± 0.7^(b) NA 0.8 ± 0.1 (SEQ ID NO: 15) PGA-PTX-c(RADfk) a2.3 ± 0.2 ^(a) 5.0 ± 0.3^(a) 4.9 ± 0.2^(b) 0.8 ± 0.2 0.9 ± 0.1PGA-PTX-c(RADfk) b 5.5 ± 0.3 ^(a) 5.0 ± 0.2^(a) 4.3 ± 0.3^(b) 1.1 ± 0.30.7 ± 0.1 SEQ ID NO: 19) PGA-PTX-c(RGDfk) 2.2 ± 0.4 ^(a) 5.0 ± 0.3^(a)4.6 ± 0.5^(b) 1.2 ± 0.3 0.9 ± 0.2 (SEQ ID NO: 16) PGA-PTX-E-[c(RGDfk)₂]a 2.6 ± 0.4 ^(a) 5.0 ± 0.1^(a) 4.7 ± 0.2^(b) 1.0 ± 0.3 0.8 ± 0.2PGA-PTX-E-[c(RGDfk)₂] b 5.5 ± 0.3 ^(a) 5.0 ± 0.3^(a) 3.9 ± 0.4^(b) 1.1 ±0.3 0.8 ± 0.2 (SEQ ID NO: 18) ^(a)Average value as determined by HPLC(indirect analysis) and UV spectroscopy (direct analysis).^(b)Determined by amino acid analysis. ^(c)Determined by HPLC. Averageof two different extraction procedures (see details above). NA: notappropriate.

Hydrodynamic Diameter and Polydispersity of the Conjugates:

The hydrodynamic diameter and size distribution of a polydispersedpopulation of nano-scale PGA-PTX−E-[c(RGDfk)₂] particles (SEQ ID NO:18)was assessed using laser light scattering microscopy with theNanoparticle Tracking Analysis (NTA) technology (NanoSight LM20™,Salisbury, UK). The mean hydrodynamic diameter of the conjugate[PGA-PTX−E-c(RGDfk)₂] (SEQ ID NO:18) with PTX loading of 5.5 mol % and-E-c(RGDfk)₂ loading of 3.9 mol % (i.e. second conjugate) was about 30nm (see, FIG. 9A). The mean hydrodynamic diameter of the conjugate[PGA-PTX−E-c(RGDfk)₂] (SEQ ID NO:18) with PTX loading of 2.6 mol % and-E-c(RGDfk)₂ loading of 5 mol % (i.e. first conjugate) was about 40 nm(see, FIG. 9B). The mean hydrodynamic diameter of the conjugate[PGA-PTX−E-c(RGDfk)] (SEQ ID NO:16) with PTX loading of 2.3 mol % andwith -E-c(RGDfk) loading of 5 mol % was about 35 nm (see, FIG. 9C).

The average molecular weight (MW), polydispersity (Mw/Mn) and thebehavior of PGA conjugates and control non-conjugated PGA in solutionwere analyzed by size exclusion chromatography (SEC). Both techniquesshowed that the PGA conjugates have a more compact conformationalstructure and greater sedimentation coefficient (S) as compared to thecontrol nonconjugated PGA. The MW was determined, by SEC, as 17700 Da(MW/Mn=1.3) for PGA and 48600 Da (MW/Mn=1.4) for the PGA-PTX−c(RGDfk)₂conjugate (SEQ ID NO:18) (the second conjugate) and 35700 Da (Mw/Mn=1.4)for PGA-E-[c(RGDfk)₂] conjugate (SEQ ID NO:15).

PTX Release from PGA Copolymer-E-c(RGD)₂-Paclitaxel Conjugate (SEQ IDNO:18) by Cathepsin B:

The ability of the conjugates of the present invention to release PTX inthe presence of preselected cellular enzymes, for instance, thelysosomal enzyme cathepsin B, was tested. The results are presented inFIG. 10 and show that the conjugates synthesized exhibited atime-dependent and drug loading dependent drug release kinetics in theenzymatic experiments. It is important to mention that in all cases themain metabolite released from the polymer was PTX as determined by LC/MSexperiments using a MALDI-TOF as MS detector. PGA-PTX−E-[c(RGDfk)₂] (SEQID NO:18; having 3.9 mol % E-[c(RGDfk)₂], 5.5 mol % PTX loadings) showedslightly faster release kinetics compared to all other conjugates,including PGA-PTX−E-c(RGDfk) (SEQ ID NO:16) (FIG. 2A). Interestingly,PTX release was greater with the second conjugate, bearing greater PTXloading (5.5 mol %) and lower E-[c(RGDfk)₂] content (3.9 mol %), after48 hours as compared to the first conjugate synthesized having a lowerPTX loading (2.6 mol %) and higher E-[c(RGDfk)₂] content (5 mol %).These differences could be due to a different conformation adopted asthese polymer conjugates form unimolecular micelles in solution. Forstability studies under hydrolytical conditions and in the presence ofplasma, non-significant PTX release was observed in the conjugatesanalyzed (data not shown).

Example 5 Synthesis of Fluorescently Labeled Conjugates

A fluorescence probe, Oregon Green-cadaverine (OG), was conjugated tothe various PGA conjugates through the free carboxylic groups, namelyPGA-OG, PGA-c(RADfk)-OG (SEQ ID NO:24) and PGA-E-[c(RGDfk)₂]-OG (SEQ IDNO:25) were synthesized in order to study the cellular uptake andtrafficking. The conjugates were dissolved in the minimum amount ofanhydrous DMF, then N,N′-diisoproprylcarbodiimmide (DIC) and1′-hydroxybenzotriazole (HOBT) were added, using a DIC/HOBT/COOH groupsmolar ratio of 1.5:1.5:1. Finally, a DMF solution of OregonGreen-cadaverine (OG) was added with a OG/COOH groups molar ratio of1:100. The reactions were monitored by TLC and eluted with MeOH followedby DMF evaporation by vacuum. The residues were dissolved in an aqueoussolution of NaHCO₃ (1.5:1 molar ratio of NaHCO₃ and the COOH groups) andloaded onto a PD10 column, eluted with water, with collecting fractionsof 1 ml to 2 μl of each fraction. 498 μl of MeOH was added to eachfraction, in order to measure the fluorescence and identify thefractions containing the PGA-OG conjugates and to quantify the amount ofconjugated OG. OG loading ranged from 0.7 to 0.9 mol %.

Example 6 Anti-Angiogenesis Activity of HPMACopolymer-c(RGDfK)₂-Paclitaxel Conjugate (SEQ ID NO:23)

The ability of Paclitaxel (PTX) and the cyclic RGD-containing peptidec(RGDfk)₂ when conjugated to the HPMA copolymer (SEQ ID NO:23), ascompared to free Paclitaxel and c(RGDfk)₂, to inhibit endothelial andtumor cell proliferation, migration towards the chemoattractant vascularendothelial growth factor (VEGF) and to adhere to a fibrinogen matrix istested in vitro.

Cell Proliferation Assay:

Human umbilical vein endothelial cells (HUVEC) or MCF7 or MCF7/Cyr61breast cancer cells are seeded on gelatinized plates. Following 24 hoursof incubation, cells are challenged with serial concentrations of eitherPTX or c(RGDfk)₂ (SEQ ID NO:26) or HPMA copolymer-c(RGDfk)₂-PTX (SEQ IDNO:23) in the presence of growth factors. Cells are counted after 72hours using Beckman Culter Counter.

Migration Assay:

A migration assay is performed in order to evaluate the effect of freePTX, or c(RGDfk)₂ (SEQ ID NO:26) or HPMA copolymer-c(RGDfk)₂-PTX (SEQ IDNO:23) on the ability of breast tumor cells, MCF7 or MCF7/Cyr61 or HUVECto migrate through endothelial cell monolayer in a transwell systemusing vascular endothelial growth factor (VEGF) as a migrationstimulator in the bottom chamber. This imitates their ability to crossthe endothelium and metastasize in vivo.

The cell migration assay is performed as described above for HUVEC.Briefly, HUVEC, MCF7 or MCF7/Cyr61 (5×10⁴ cells/100 μl) are challengedwith free PTX, c(RGDfk)₂ (SEQ ID NO:26), or HPMA copolymer-c(RGDfk)₂-PTX(SEQ ID NO:23), and are then plated on the upper chamber of thetranswell for a 2 hours incubation period. Following incubation, cellsare allowed to migrate to the underside of the chamber in the presenceor absence of VEGF in the lower chamber. Cells are then fixed andstained and the number of migrated cells per membrane is determined.Migration is normalized to percent migration, with 100% representingVEGF dependent migration of cells which are not incubated with anycompound.

Endothelial Cell Adhesion Assay:

The ability of c(RDGfk)₂ (SEQ ID NO:26), c(RDGfk)₂-Paclitaxel (SEQ IDNO:49) and HPMA copolymer-c(RGDfk)₂-Paclitaxel conjugate (SEQ ID NO:23)to inhibit endothelial cell adherence to a fibrinogen coated matrix isdetermined. Trypsinized HUVEC are incubated with the tested conjugateand with the inactive c(RADfk)₂ (SEQ ID NO: 50) or c(RADfk)₂-Paclitaxel(SEQ ID NO: 51) as controls. The treated HUVECs are then plated onfibrinogen-coated 96-well culture plates and allowed to attach. Theattached cells are then fixed and dyed and their number is determinedusing Nikon TE2000E inverted microscope and NIH image software.

Example 7 Binding of PGA-Conjugated c(RGDfK)₂ to the αvβ₃ IntegrinReceptor

αvβ₃ integrin expression on HUVEC, U87 glioblastoma and PANC02 cells wasdetermined using αvβ₃ integrin immunostaining and FACS. αvβ₃ integrinwas highly expressed on HUVEC and U87 glioblastoma cells, but was absentfrom PANC02 cells (see, FIG. 11A).

Using amnis ImageStream 100 imaging flow cytometer and the fluorescenceprobe Oregon Green-cadaverine (OG), the interaction of PGA-OG,PGA-c(RADfk)-OG (SEQ ID NO:24) and PGA-E-[c(RGDfk)_(2])-OG (SEQ IDNO:25) with αvβ₃ integrin receptor of the conjugates was evaluated inHUVEC. Conjugate-cell adherence was observed for PGA-E-[c(RGDfk)₂]-OG(SEQ ID NO:25) as early as 10 minutes following cell incubation with theconjugate, which further continued to enhance, thereby suggesting cellinternalization of the conjugate. PGA-c(RADfk)-OG (SEQ ID NO:24) startedadhering to cell surface a little later, at 15 minutes (see, FIGS. 11Band 11C). In contrast, the conjugate which did not comprise the RGDmoiety (PGA-c(RADfk)-OG; SEQ ID NO:24) bound to a much lesser extent tothe cells (see, FIG. 11B), thereby demonstrating a role for the RGDmoiety in the interaction and subsequent internalizations of theconjugates into the cells, most likely via the αvβ₃ integrin receptor.

Example 8 Anti-Angiogenesis Activity ofPGA-Copolymer-E-[c(RGDfk)₂]-Paclitaxel Conjugate (SEQ ID NO:18) CellProliferation Assay

In order to evaluate whether similar to PTX, c(RGDfk)₂ (SEQ ID NO: 26)and PGA-E-[c(RGDfk)₂]-PTX, (SEQ ID NO:18) a representative conjugateaccording to the embodiments of the present invention, possessesanti-angiogenic properties, HUVEC proliferation, capillary-like tubeformation and migration assays were performed. The cyclic peptidec(RADfk) (SEQ ID NO:40) served as a negative control for the-E-[c(RGDfk)₂] (SEQ ID NO:2) since this peptide has low affinity bindingto integrin receptors. The activity of the PGA-E-[c(RGDfk)_(2])-PTXconjugate (SEQ ID NO:18) was compared to the activity of thepolyglutamate polymer alone (PGA), Paclitaxel alone (PTX), a conjugateof PGA-PTX, a conjugate of PGA with the negative control RAD containingpeptide (PGA-c(RADfk); SEQ ID NO:14) and a conjugate of PGA with thebis-cyclic RGD-containing peptide (PGA-E-c(RGDfk)₂; SEQ ID NO:15). Thechemical structure of these conjugates is presented in FIG. 2. Theactivity of the PGA-E-[c(RGDfk)₂]-PTX conjugate (SEQ ID NO:18) was alsocompared to a similar conjugate only with the RGD-containing peptidebeing replaced by the negative control RAD peptide (SEQ ID NO:19)(chemical structures of these two conjugates are presented in FIG. 3).The IC₅₀ values measured for the tested conjugates are presented inTable 2. Table 2 presents data for 5 experiments performed, whereby ineach experiment the IC₅₀ of the various compounds (detailed on the leftcolumn) were compared to the IC₅₀ of a specific conjugate using aspecific cell line (as indicated in the upper first and second rows).When the conjugate comprised only one RGD moiety than it was compared tocontrol compounds comprising only one RGD moiety (i.e. the x in Table 2equals 1). When the conjugate comprised two RGD moieties than it wascompared to control compounds also comprising two RGD moieties (i.e. thex in Table 2 equals 2).

The proliferation of HUVEC was inhibited similarly by the PGA-PTX,PGA-PTX−E-[c(RGDfk)₂] (SEQ ID NO:18) and PGA-PTX−c(RADfk) (SEQ ID NO:19)conjugates at PTX equivalent concentrations in which more than 50% ofthe cells were inhibited at concentrations lower than 0.2 and higherthan 17 nM (see, FIG. 12A). Free PTX by itself and in combination withE-[c(RGDfk)₂] (SEQ ID NO:2) or c(RADfk) (SEQ ID NO:40) inhibited HUVECproliferation more efficiently, demonstrating an IC₅₀ value of about0.01 nM PTX. E-[c(RGDfK)₂] peptide, alone (SEQ ID NO:2) or conjugated toPGA (SEQ ID NO:15), inhibited HUVEC proliferation by itself but only athigh concentrations. c(RADfk) peptide (SEQ ID NO:40), or PGA showed noeffect even at those high concentrations (for IC₅₀ values see, Table 2).

For U87 cells, another αvβ₃ expressing cell type, proliferationinhibition was very similar to that of HUVEC. Free PTX, or combined withE-[c(RGDfk)₂] (SEQ ID NO:2) or c(RADfk) (SEQ ID NO:40) at equivalentdoses had similar effect, exhibiting an IC₅₀ of about 0.01 nM PTX, as itwas for HUVEC. Moreover, PGA-PTX, PGA-PTX−E-[c(RGDfk)₂] andPGA-PTX−c(RADfk) conjugates (SEQ ID NOs:18 and 19 respectively) atequivalent doses had an exact similar bell-shaped effect, as was seen onHUVEC, in which more than 50% of the cells were inhibited atconcentrations lower than about 0.055 and higher than 70 nM PTX (FIG.12B).

A different inhibition pattern was seen for the non-expressingαvβ₃PANC02 cells. Free PTX, or combined with E-[c(RGDfk)₂] or c(RADfk)(SEQ ID NOs:2 and 40 respectively) at equivalent doses inhibited cellsproliferation with an IC₅₀ of about 200 nM PTX. As apposed to HUVEC andU87 cells, PGA-PTX−E-[c(RGDfk)₂] conjugate (SEQ ID NO:18) had a moresignificant effect with IC₅₀ of about 650 nM PTX, were PGA-PTX andPGA-PTX−c(RADfk) (SEQ ID NO: 19) had an IC₅₀ of about 2000 nM PTX (FIG.12C). On these cells, bell-shaped pattern of conjugate inhibition wasnot observed.

These results show that the anti-angiogenesis agent Paclitaxelmaintained its anti-proliferative activity when conjugated, togetherwith the angiogenesis targeting moiety c(RGDfk)₂ (SEQ ID NO:26), to aPGA polymer.

TABLE 2 IC50 (nM) of IC50 (nM) of IC50 (nM) of IC50 (nM) of IC50 (nM) ofPGA-PTX-E- PGA-PTX-E- PGA-PTX-E- PGA-PTX-E- PGA-PTX-E- c(RGDfk)[c(RGDfk)₂] [c(RGDfk)₂] [c(RGDfk)₂] [c(RGDfk)₂] (SEQ ID NO: 16)(SEQ ID NO: 18) (SEQ ID NO: 18) (SEQ ID NO: 18) (SEQ ID NO: 18)2.1 mol % PTX, 2.6 mol % PTX, 5 mol % PTX, 5 mol % PTX, 5 mol % PTX,5 mol % RGD 5 mol % RGD 3.9 mol % RGD 3.9 mol % RGD 3.9 mol % RGDCell type HUVEC HUVEC HUVEC U87 PANCO2 PGA NA NA NA NA NA c(RADfK) NA NANA NA NA (SEQ ID NO: 40) E-[c(RGDfK)_(X)] NA 8000 4000 NA NA X = 1 or 2(SEQ ID NOs: 41 or 2 respectively) PTX 0.0085 0.01 0.009 0.045 200PGA-E-[c(RGDfK)_(X)] NA 2900 7000 NA NA X = 1 or 2 (SEQ ID NOs: 17 or15respectively) PGA-c(RADfK) 1000 5000 NA NA NA (SEQ ID NO: 14) PGA-PTX0.38-10 0.23-20  0.4-15 0.1-80 2000 PTX+ c(RADfK) 0.0085 0.02 2 0.9 110(SEQ ID NO: 40) PTX+ 0.006 0.017 0.05 0.07 680 E-[c(RGDfK)_(X)] X =1 or 2 (SEQ ID NOs: 41 or 2 respectively) PGA-PTX-c(RADfK) 0.42-100.19-19 0.38-18 65 2600 SEQ ID NO: 19 PGA-PTX-E- 0.28-20 25  0.2-180.055-70 650 [c(RGDIK)_(X)] X = 1 or 2 (SEQ ID NOs: 16 or18respectively) IC₅₀ values for all the compounds and all combinationswere calculated from the proliferation assays results. The presenteddata is for the different loading percentage of PTX and the differentloading percentage of E-[c(RGDfk)₂] or E-c(RGDfk). NA-Non applicable,did not reach IC₅₀ in the concentrations used.

Similar results on HUVEC proliferation were obtained for thePGA-PTX−E-[c(RGDfk)₂] conjugate (SEQ ID NO:18) having a 5 mol %E-[c(RGDfk)₂] and 2.6 mol % PTX loading (see, FIG. 13A) as well as forthe PGA-PTX−E-c(RGDfk) conjugate (SEQ ID NO:16) (see, FIG. 13B) wherebyboth showed a similar bell shaped effect, with an IC₅₀ of ˜0.2 and 20 nMPTX respectively.

Example 9

Anti-Angiogenesis Activity of PGA-Copolymer-E-[c(RGDfK)₂]-PaclitaxelConjugate (SEQ ID NO:18)

Migration Assay

Next, the effect of PGA-E-[c(RGDfk)₂]-PTX conjugate (SEQ ID NO:18) onthe ability of HUVEC to migrate towards VEGF was tested.PGA-E-[c(RGDfk)_(2])-PTX conjugate (SEQ ID NO:18; 5 mol % E-[c(RGDfk)₂],2.6 mol % PTX loadings i.e. second conjugate synthesized) XXX PLEASECONFIRM—yes at equivalent concentrations of 100 nM PTX, inhibited themigration of HUVEC towards VEGF by about 40% (see, FIG. 14). PTX alone,the combination of PTX and -E-[c(RGDfk)₂] (SEQ ID NO:2) or c(RADfk) (SEQID NO:40) and PGA-PTX conjugate had greater inhibitory effect of about55%. PGA served as control and had no inhibitory effect on the abilityof HUVEC to migrate towards VEGF while -E-[c(RGDfk)₂] (SEQ ID NO:40) andc(RADfk) (SEQ ID NO: 40) had an inhibitory effect of about 30%.

These results show that the anti-angiogenesis agent Paclitaxel as wellas the c(RGDfk)₂ peptide (SEQ ID NO: 26) both inhibited endothelial cellmigration, although the latter to a lesser extent. Furthermore,Paclitaxel inhibition ability was preserved when conjugated togetherwith c(RGDfk)₂ (SEQ ID NO:26) to the PGA.

Example 10 Anti-Angiogenesis Activity ofPGA-Copolymer-E-[c(RGDfK)₂]-Paclitaxel Conjugate (SEQ ID NO:18)Endothelial Cell Adhesion Assay

One of the principle stages of angiogenesis involves the adhesion ofendothelial cell to the extracellular matrix and is mediated throughintegrin receptors. Therefore, drugs which interact and inhibit theactivity of the integrin receptor inhibit endothelial cell adhesion andconsequently, serve as antiangiogenesis agents. α_(v)β₃ integrins areknown to bind the RGD sequence (Arg-Gly-Asp; SEQ ID NO:1), whichconstitutes the recognition domain of different proteins, such aslaminin, fibronectin and vitronectin. Tumor-induced angiogenesis can betargeted in vivo by antagonizing the αvβ₃ integrin with small peptidescontaining the RGD amino acid sequence (SEQ ID NO:1).

Therefore, endothelial cell adhesion assay was performed in order toevaluate in vitro the targeting specificity (i.e. ability to bind to theintegrin receptors) of the cyclic RGD containing peptides -E-[c(RGDfk)₂](SEQ ID NO:2) or c(RGDfk) (SEQ ID NO:9) when conjugated to PTX and PGA.

Presented in FIG. 15 are bar graphs of the percent of observed celladhesion of HUVEC to fibrinogen coated plates when incubated with one ofthe tested compounds. The results were normalized to the percent of celladhesion when no compound was added. All RGD-bearing PGA-PTX conjugatesat equivalent concentrations of 50 μM RGD were able to inhibit HUVECadhesion to fibrinogen by ˜60%. PGA-PTX−c(RADfk) conjugate (SEQ IDNO:19) served as control to each RGD conjugate. When PGA-PTX−c(RADfk)conjugate (SEQ ID NO:19) was compared to bis-cyclic RGD-bearingconjugates, with a similar amount of PTX, it had a minor inhibitoryeffect of ˜20%. When it was compared to monocyclic RGD-bearingconjugate, with a similar amount of PTX, it inhibited HUVEC adhesion aswell as PGA-PTX−E-c(RGDfk) (SEQ ID NO:16) (˜50%). Free PTX, as PGA, andall their combinations, had a negligent effect on endothelial celladhesion. The free peptides E-[c(RGDfK)₂] (SEQ ID NO:2) or E-c(RGDfk)(SEQ ID NO:41) and c(RADfK) (SEQ ID NO:40) served as controls. Asexpected, the RGD peptidomimetics completely abrogated HUVEC adhesion at50 μM while at the same concentration the c(RADfK) peptide (SEQ IDNO:40) had no effect on the adhesion of the cells

The first PGA-PTX−E-[c(RGDfk)₂] conjugate (SEQ ID NO:18; having aloading of 3.9 mol % E-[c(RGDfk)₂] and 5.5 mol % PTX) was more effectivethan the second PGA-PTX−E-[c(RGDfk)₂] conjugate synthesized (SEQ IDNO:18; having a loading of 5 mol % E-[c(RGDfk)₂], and 2.6 mol % PTX).Both conjugates inhibited the adhesion more effectively than themonocyclic RGDfk peptide conjugate PGA-PTX−E-c(RGDfk) (SEQ ID NO:16).

These results show that the cyclic peptides E-[c(RGDfk)₂] (SEQ ID NO:2)and c(RGDfk) (SEQ ID NO:9) maintained the ability to bind α_(v)β₃integrins and inhibit endothelial cell adhesion when conjugated togetherwith PTX to a PGA polymer (SEQ ID NOs: 18 and 16 respectively.

Example 11 Anti-Angiogenesis Activity ofPGA-Copolymer-E-[c(RGDfk)₂-Paclitaxel Conjugate (SEQ ID NO:18)Capillary-Like Tube Formation of Endothelial Cells In Vitro

Having shown that conjugated PTX and [c(RGDfk)₂] (SEQ ID NO: 26) haveanti-angiogenic potential by inhibiting the proliferation, adhesion andmigration of HUVEC, the effect of the PGA-E-[c(RGDfk)_(2])-PTX conjugate(SEQ ID NO:18) on the ability of HUVEC to form capillary-like tubestructures on Matrigel was examined (see, FIG. 16). This assay aims toimitate the capability of endothelial cells to form 3-D vascularstructures in vivo as an important step in the angiogenic cascade.PGA-E-[c(RGDfk)₂]-PTX conjugate (SEQ ID NO:18; 5 mol % E-[c(RGDfk)₂],2.6 mol % PTX loadings i.e. second conjugate synthesized),PGA-c(RADfk)-PTX conjugate (SEQ ID NO:19) as control, and thecombinations of PTX and E-[c(RGDfk)₂] (SEQ ID NO:2) at equivalentconcentrations of 10 nM and 19 nM, respectively, inhibited the formationof tubular structures of HUVEC by about 40% (see, FIG. 16B). PTX alonehad greater inhibitory effect of about 50% and PGA, which served ascontrol, had no inhibitory effect on the ability of HUVEC to formtubular structures.

These results show that Paclitaxel maintained its inhibitory effect onthe ability of endothelial cell to form capillary-like tube structures,when conjugated with E-[c(RGDfk)₂] to a PGA polymer (SEQ ID NO:18).

Example 12 Specific Antagonism of αvβ₃

Cyr61 (also known as CCN1) is a Cysteine-rich matricellular protein thatsupports cell adhesion and induces adhesion signaling. Furthermore,Cyr61 stimulates endothelial cell migration and enhances growth factorinduced DNA synthesis in culture and therefore induces angiogenesis invivo. Mechanistically, Cyr61 acts as a non-RGD-containing ligand ofintegrin receptors. Functional blockade of αvβ₃, a Cyr61 integrinreceptor, is specifically cytotoxic towards Cyr61-overexpressing breastcancer cells and a specific αvβ3-RGD peptidomimetic agent (SEQ ID NO:28)prevents αvβ3 from binding to its ligand, Cyr61.

The ability of HPMA copolymer-c(RGDfk)₂-Paclitaxel conjugate (SEQ IDNO:23), PGA copolymer-E-c(RGDfk)₂-Paclitaxel (SEQ ID NO:18) and thepolymer PGA copolymer-E-c(RGDfk)-Paclitaxel conjugate (SEQ ID NO:16) toact as a specific antagonist of αvβ3 and thus to inhibit theCyr61-integrin receptor signal transduction cascade is evaluated inCYR61-overexpressing and control MCF-7 cells.

Downregulation of PI-3′K and ERK1/ERK2 Cascades:

Some of the phenotypic changes dictated by the Cyr61-driven αvβ3signaling, like enhanced endothelial cell survival and proliferation,are dependent upon activation of phosphatidylinositol 3′-kinase(PI-3′K/AKT) and ERK1/ERK2 MAPK cascades. Those pathways were recentlyfound to be unregulated in Cyr61-overexpressing MCF-7 cells. Based onthose findings, the same cell line is used to analyze the efficacy ofthe conjugates as αvβ₃ antagonists. Protein extracts are prepared fromCyr61-overexpressing MCF-7 cells before and after treatment with theconjugates, and the levels of PI-3′K/AKT and ERK1/ERK2 MAPK activationis monitored by Western blot.

Enhancement of the Apoptosis Level:

Functional blockade of αvβ₃ synergistically enhances Paclitaxel-inducedapoptosis in Cyr61-overexpressing breast cancer cells. Thus, theapoptosis level of Cyr61-overexpressing and control MCF-7 cells isanalyzed by flow cytometry, before and after treatment with theconjugates. Cell extracts are also analyzed by Western blot for theexpression level of different apoptotic proteins, like Bax, cleaved-PARPand several caspases.

p53 Accumulation:

Paclitaxel-induced apoptosis involves a dose- and time-dependentaccumulation of the tumor suppressor p53. αvβ₃ hyperactivation by Cyr61overexpression impairs Paclitaxel-induced accumulation of p53. Usingwestern blotting techniques, the level of p53 protein, in cell extractsof CYR61-overexpressing MCF-7 cells in the presence/absence of theconjugates is evaluated.

Example 13 Evaluation of Antitumor Activity of the Conjugates in MiceBearing Mammary Tumors

Paclitaxel has already been used successfully in the treatment of breastcancer both in animal models and in the clinic. SCID mice bearing MCF orMCF/Cyr61-Luciferase breast cancer cells in the mammary fat pad aretreated with free Paclitaxel, Paclitaxel-c(RDGfk)₂ conjugate (SEQ IDNO:49), HPMA copolymer-c(RGDfk)₂-Paclitaxel conjugate (SEQ ID NO:23),PGA copolymer-E-c(RGDfk)-Paclitaxel (SEQ ID NO:16) or PGAcopolymer-E-c(RGDfk)₂-Paclitaxel (SEQ ID NO:18), in the followingmanner: the animals are treated with one of the tested drugs at aequivalent dose of Paclitaxel (5 mg/kg weekly). Animals treated withsaline, HPMA copolymer, PGA or c(RDGfk)₂ (SEQ ID NO:26) are used ascontrols. The animals are monitored daily for general health, weightloss and tumor progression. Once a week the mice are imaged followingadministration of luciferase i.v. using the Biospace Photon Imager inorder to follow up the tumor progression. All treatments are evaluatedat three time points: (i) early treatment at the hyperplasic stage (10days after tumor cells inoculation) in order to block the angiogenicswitch before the initial formation of solid tumors (prevention trial),(ii) treatment of mice bearing small (asymptomatic) solid tumors (15-30days after tumor cells inoculation) in order to determine whether theirexpansive growth and progression to deleterious stages could beinhibited (intervention trial), and (iii) treatment of mice withsubstantial tumor burden and near death (around 45 days after tumorcells inoculation) to ascertain whether these conjugates can inducetumor regression (regression trial). At termination, animals areexamined by post-mortem; tumors are dissected and analyzed by: a)immunohistochemistry: PCNA for proliferation, TUNEL for apoptosis, CD-31for vessel density quantification; b) ELISA of angiogenic growth factors(VEGF, bFGF, TGF-β) to evaluate the effects of the therapy on thoseangiogenic factors and prognosis markers (kits by R&D); c) FACS analysisand Western blotting to determine the αvβ₃ expression andphosphorylation changes before and after therapy.

Example 14 Evaluation of Antitumor Activity of the PGA-PTX−E-[c(RGDfK)₂]Conjugate in Mice Bearing Human Osteosarcoma Tumors

In vivo evaluation of RGD-bearing conjugates was preformed in twomethods: First, confocal microscopy analysis of mCherry labeled tumorsdissected from mice treated with PGA-E-[c(RGDfk)_(2])-OG (SEQ ID NO: 25)revealed high accumulation of the conjugate at the tumor site, asopposed to PGA-c(RADfk)-OG (SEQ ID NO:24) or PGA-OG conjugates (see,FIG. 17A). Second, the mCherry-labeled-MG63 cells from homogenizedtumors treated with PGA-PTX-OG different conjugates were FACS-sorted byImageStrim. The results show that PGA-PTX−E-[c(RGDfk)₂]-OG (SEQ IDNO:25) efficiently interacts with tumor cells compared withPGA-PTX−c(RADfk)-OG (SEQ ID NO:24) and PGA-PTX-OG (see, FIG. 17B).

Although the invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, it is intended to embrace all such alternatives,modifications and variations that fall within the spirit and broad scopeof the appended claims.

All publications, patents and patent applications mentioned in thisspecification are herein incorporated in their entirety by referenceinto the specification, to the same extent as if each individualpublication, patent or patent application was specifically andindividually indicated to be incorporated herein by reference. Inaddition, citation or identification of any reference in thisapplication shall not be construed as an admission that such referenceis available as prior art to the present invention. To the extent thatsection headings are used, they should not be construed as necessarilylimiting.

1-42. (canceled)
 43. A conjugate comprising a polymeric backbone havingattached thereto a therapeutically active agent and an angiogenesistargeting moiety, said angiogenesis targeting moiety comprising a leastone Arg-Gly-Asp (RGD)-containing moiety, and said therapeutically activeagent being selected from the group consisting of paclitaxel andTNP-470.
 44. The conjugate of claim 43, wherein said polymeric backboneis derived from a polyglutamic acid (PGA).
 45. The conjugate of claim43, wherein said polymeric backbone is derived from a polymer selectedfrom the group consisting of dextran, a water soluble polyamino acid, apolyethylenglycol (PEG), a polyglutamic acid (PGA), a polylactic acid(PLA) a polylactic-co-glycolic acid (PLGA), apoly(D,L-lactide-co-glycolide) (PLA/PLGA), apoly(hydroxyalkylmethacrylamide), a polyglycerol, a polyamidoamine(PAMAM), and a polyethylenimine (PEI).
 46. The conjugate of claim 43,wherein said angiogenesis targeting moiety comprises at least twoRGD-containing moieties, said moieties being the same or different. 47.The conjugate of claim 43, wherein said RGD-containing moiety isc[Arg-Gly-Asp-Phe-Lys].
 48. The conjugate of claim 43, wherein at leastone of said therapeutically active agent and said targeting moiety isattached to said polymeric backbone via a linker.
 49. The conjugate ofclaim 48, wherein said linker is a biodegradable linker.
 50. Theconjugate of claim 49, wherein said biodegradable linker is selectedfrom the group consisting of a pH-sensitive linker and anenzymatically-cleavable linker
 51. The conjugate of claim 49, whereinsaid biodegradable linker is an enzymatically cleavable linker.
 52. Theconjugate of claim 51, wherein said enzymatically cleavable linker iscleaved by an enzyme which is overexpressed in tumor tissues.
 53. Theconjugate of claim 51, wherein said linker comprises a-[Gly-Phe-Leu-Gly]-moiety.
 54. The conjugate of claim 51, wherein saidlinker comprises -[Gly-Pro-Leu-Gly-Ile-Ala-Gly-Gln]-.
 55. The conjugateof claim 43, wherein at least one of said therapeutically active agentand said angiogenesis targeting moiety is attached to said polymericbackbone and/or to said linker via a spacer.
 56. The conjugate of claim43, wherein said anti-angiogenesis agent is Paclitaxel and saidangiogenesis targeting moiety comprises a c[Arg-Gly-Asp-Phe-Lys] moiety.57. The conjugate of claim 43, wherein said anti-angiogenesis agent isPaclitaxel and said angiogenesis targeting moiety comprises twoc[Arg-Gly-Asp-Phe-Lys] moieties.
 58. The conjugate of claim 57, havingthe structure:

wherein: x is an integer having a value such that x/(x+y+w) multipliedby 100 is in the range of from 0.01 to 99.9; y is an integer having avalue such that y/(x+y+w) multiplied by 100 is in the range of from 0.01to 99.9; and w is an integer having a value such that w/(x+y+w)multiplied by 100 is in the range of from 0.01 to 99.9.
 59. Theconjugate of claim 57, having the structure:

wherein: x is an integer having a value such that x/(x+y+w) multipliedby 100 is in the range of from 70 to 99.9; y is an integer having avalue such that y/(x+y+w) multiplied by 100 is in the range of from 0.01to 15; and w is an integer having a value such that w/(x+y+w) multipliedby 100 is in the range of from 0.01 to
 15. 60. The conjugate of claim43, further comprising a labeling agent attached thereto.
 61. Aconjugate comprising a polymeric backbone having attached thereto atherapeutically active agent and an angiogenesis targeting moiety, saidangiogenesis targeting moiety comprising a least one Arg-Gly-Asp(RGD)-containing moiety, and said therapeutically active agent beingselected from the group consisting of an anti-angiogenesis agent and ananti-cancer agent.
 62. The conjugate of claim 61, wherein saidangiogenesis targeting moiety comprises at least two RGD-containingmoieties, said moieties being the same or different.
 63. The conjugateof claim 61, wherein said RGD-containing moiety isc[Arg-Gly-Asp-Phe-Lys].
 64. The conjugate of claim 61, wherein at leastone of said therapeutically active agent and said targeting moiety isattached to said polymeric backbone via a linker.
 65. The conjugate ofclaim 64, wherein said linker is an enzymatically cleavable linker whichis cleaved by an enzyme which is overexpressed in tumor tissues.
 66. Theconjugate of claim 61, further comprising a labeling agent attachedthereto.
 67. A pharmaceutical composition comprising, as an activeingredient, the conjugate of claim 43 and a pharmaceutically acceptablecarrier.
 68. The pharmaceutical composition of claim 67, being packagedin a packaging material and identified in print, in or on said packagingmaterial, for use in the treatment of a medical condition associatedwith angiogenesis.
 69. The pharmaceutical composition of claim 68,wherein said conjugate comprises a labeling agent, the composition beingpackaged in a packaging material and identified in print, in or on saidpackaging material, for use in monitoring a medical condition associatedwith angiogenesis.
 70. The pharmaceutical composition claim 68, whereinsaid condition is selected from a group consisting of atherosclerosis,cancer, hypertension, rheumatoid arthritis, diabetes and diabetesrelated complications.
 71. A pharmaceutical composition comprising, asan active ingredient, the conjugate of claim 61 and a pharmaceuticallyacceptable carrier.
 72. The pharmaceutical composition of claim 71,being packaged in a packaging material and identified in print, in or onsaid packaging material, for use in the treatment of a medical conditionassociated with angiogenesis.
 73. The pharmaceutical composition ofclaim 71, wherein said conjugate comprises a labeling agent, thecomposition being packaged in a packaging material and identified inprint, in or on said packaging material, for use in monitoring a medicalcondition associated with angiogenesis.
 74. A method of treating amedical condition associated with angiogenesis in a subject in needthereof, the method comprising administering to the subject atherapeutically effective amount of the conjugate of claim
 43. 75. Amethod of monitoring the level of angiogenesis within a body of apatient, the method comprising: administering to the patient theconjugate of claim 60; and employing an imaging technique for monitoringa distribution of the conjugate within the body or within a portionthereof.
 76. The method of claim 74, wherein said condition is selectedfrom the group consisting of atherosclerosis, cancer, hypertension,rheumatoid arthritis, diabetes and diabetes related complications.
 77. Amethod of treating a medical condition associated with angiogenesis in asubject in need thereof, the method comprising administering to thesubject a therapeutically effective amount of the conjugate of claim 61.78. A method of monitoring the level of angiogenesis within a body of apatient, the method comprising: administering to the patient theconjugate of claim 65; and employing an imaging technique for monitoringa distribution of the conjugate within the body or within a portionthereof.
 79. The method of claim 74, wherein said condition is selectedfrom the group consisting of atherosclerosis, cancer, hypertension,rheumatoid arthritis, diabetes and diabetes related complications.
 80. Aprocess of synthesizing the conjugate of claim 43, the processcomprising: (a) co-polymerizing a plurality of monomeric units of saidpolymer, at least one of said monomeric units terminating by a firstreactive group, and at least one of said monomeric units terminating bya second reactive group, to thereby obtain a co-polymer that comprises aplurality of backbone units, at least one backbone unit having saidfirst reactive group and at least one backbone unit having said secondreactive group, said first reactive group being capable of reacting withsaid angiogenesis targeting moiety and said second reactive beingcapable of reacting with said therapeutically active agent; (b) reactingsaid co-polymer with said angiogenesis targeting moiety or a derivativethereof, via said first reactive group, to thereby obtain a copolymerhaving said angiogenesis targeting moiety attached to a polymericbackbone thereof; and (c) further reacting said co-polymer with saidtherapeutically active agent or a derivative thereof, via said secondreactive group, to thereby obtain said co-polymer having saidtherapeutically active agent attached to a polymeric backbone thereof,thereby obtaining the conjugate of claim
 43. 81. The process of claim80, wherein at least one of said monomer units terminating by said firstor said second reactive group further comprises a linker linking saidreactive group to said monomeric unit.